After you complete the four trials in the Great Plateau shrines, you can get the paraglider from the old man.
Complete the Shrine Trials
The old man promised to give you the paraglider if you complete the shrine trials, so if you haven't already, you need to find the Great Plateau Shrines and complete the Bomb Trial, Stasis Trial, and Cryonis Trial.
Find the Old Man
After you complete the four shrine trials, the old man will meet you and tell you to go to the place where two lines drawn between the four shrines would intersect. You can press Select to look at your map to find where those lines would intersect.
When you go there, check on the glowing statue inside. You can choose to either get another Heart Container or increase your Stamina Wheel. Probably a Heart Container is more useful at this point. If you ever change your mind, there is someone you can find later in the game who will let you pay to trade a Heart Container for a Stamina Wheel upgrade and vice versa.
After you receive the upgrade, the old man speaks to you. He is on the roof. There is a ladder on the east side of the building that you can climb to reach the roof. From there, go northeast to reach a small room where you find the old man. When you go into the room, a cut scene begins. During the cut scene, the old man tells you to go east to Kakariko Village and meet with Impa. The Sheikah Slate will show you the location of the village.
After the cut scene, the old man gives you the paraglider. This completes the Isolated Plateau quest. After some dialogue, the Destroy Ganon quest and the Seek Out Impa quest is added to your Adventure Log.
After You Get the Paraglider
If you didn't open the chest in this room earlier, do so now to receive the Soldier's Bow.
You can now use the Paraglider to leave the Great Plateau. New features will be unlocked when you land outside of the Great Plateau, such as the amiibo Rune.
At this point, you are free to explore. The old man said to seek out Impa in Kakariko Village, which is to the east. That is what you should do if you want to continue the main story. You can also just explore Hyrule, finding more towers to activate so you can add to your map of Hyrule. There are also many shrines to discover.