After you get the first token of love, you can get the key that gives access to the second one.
You will want to have at least 70 olives before you go to the next part of the game. Athens is a decent place to do this, because you can use flames from the Staff of Fennel to quickly get rid of the scorpions and satyrs that attack.
Get a Password
After getting the key from Keleos and gathering olives, you can go back to Athena to get a new password if you want. (This way, if you need to use Retry after a Game Over, you will still have the key and all the olives that you collected.)
After that, go to the left through Athens and go through the door at the end to reach Eleusis (where you rescued the boy from the Lamia before). Go to the right until you see Gaea sitting up on the ledge. Equip the Ocarina and press SELECT to play it, and Gaea will wake up.
Gaea will stand up and start throwing rocks, much like Cyclops. It moves more slowly than Cyclops, but it can jump. The easiest way to fight it is to wake it up, then go to the left, where there is a low ledge that you can jump onto. Stand in the middle of this ledge so that you won't go to the upper ledge when you jump. From this ledge, if Gaea is on the ground below the ledge, you can hit Gaea directly in the face. Just jump over Gaea's rock, then hit Gaea after each rock. Gaea will die after you hit it five times with the Sword.
After Gaea is dead, go to the right, where a new door has appeared. Go through this door to arrive in Phthia.
Get an Ambrosia
In Phthia, there are more birds that drop rocks on you, and there are caterpillars that quickly go back and forth when you come near (but they roll up and stop moving when you are far away), and there are also monkeys that will jump from ledges toward you, making this a very difficult place to get through.
From the first screen, go to the left to reach the next screen. Jump to the left to land on the ledge with the stairs. Go down those stairs.
Go to the left and make your way across the ledges until you see a door. Go into that door to find a fountain. Use it to refill your health.
Exit the fountain room and go up both sets of stairs. In the upper part of Phthia, go to the left to reach the next screen, then jump onto the ledge to the left. Then go to the right, jumping onto the highest ledge on the right. From there, go right to go back to the last screen. Go to the right along the ledges and you will find a door. Go in and talk to the old man to get a free Ambrosia.
Get the Divine Sword
Exit the old man's cave and jump onto the ledge to the left. Go left and jump to the upper ledge (it's a difficult jump, so make sure to jump at the last possible moment.) Keep going left to the next area, then continue going left until you reach a door. Go in and you will find Hephaestos's temple. Talk to him and pay 70 olives to get the Divine Sword. It's the strongest weapon in the game. You can hold Up when you attack to shoot a lightning bolt, but this will deplete your health each time you do it.
Get Past the Centaur
Talk to Hephaestos again to get a password. Then exit his temple and make your way to the right. At the right side of the area, go to the lower ledge and go to the right to reach the next area. Go down the stairs to go to the next area.
Go down both sets of stairs if you want to go to the fountain room. Then, from the fountain room, go up one flight of stairs, then make your way to the right. You can jump while walking to jump higher, if you are having trouble reaching the upper ledge. Use the stairs on the right to go back to the upper area.
Go to the right and you will see the door that leads back to Attica. You might want to go there so you can visit Athena's temple and get a password.
From the door to Attica, go up the stairs, then make your way to the right. Go up both sets of stairs to reach a new area. From there, go to the right and you will encounter the Centaur. You do not actually have to kill the Centaur. There is no benefit to doing so. The Centaur shoots arrows, and it jumps up and down, as well as back and forth. The Centaur's upper body is vulnerable. You can shoot beams from the Divine Sword at the Centaur, but it will deplete your health if you do. It's best to hit the Centaur's upper body when it is coming toward you, because if you hit it successfully, it will move back instead of continuing to come toward you, and it also can't hurt you for a moment after you hit it (which gives you an opportunity to run past it if you wish, but be careful of the monkey in the right side of the area). If you move toward or away from the Centaur, it will change its jumping distance, possibly jumping much farther toward you and therefore becoming much more likely to hit you. So try not to move forward or back (except to avoid falling rocks from birds) and just focus on jumping up to hit the Centaur's upper body when it is coming toward you.
Get the Second Token
Whether you decided to fight the Centaur or ignore it, go to the right side of the area, where there is a waterfall. Go up to the highest ledge, then go to the right and press up while you fall. You should enter a secret door in the upper part of the waterfall. (If you are in the lower part of the dark cave, you went into the wrong secret door. Go back outside and try to enter the upper secret door in the waterfall.)
Once you are in the upper part of the dark cave, go to the right and use the Eye of the Graeae. If it doesn't reveal a secret door, go farther to the right and try again. Once you reveal the secret door, go inside. There is a locked door on the right, but if you got the key from Keleos, it will slide open when you go toward it. Go inside and you will find a Nymph, who will give you the second Token of Love and a letter from Helene. She says that the entrance to Hades's realm is along the sea between Crete and Argolis. After you read Helene's message, the Nymph will disappear.