Starting on day 22 of Spring, Year 1, Veronica removes the roadblocks to the rental field areas. You can talk to Veronica in the guild to rent a field.
Unlock Field Rental
Field rental is automatically unlocked on day 22 of Spring, Year 1. On that day, there will be an automatic cut scene where Veronica will invite you to the Guild and explain about renting fields.
To rent a field, talk to Veronica in the guild and choose the field that you want to rent. You can't rent fields that other farmers are renting, although later in the year you will be able to do Conquests to gain control of other fields.
Extend Your Lease
On the day that your lease is about to expire, a message will pop up when you wake up to notify you about the expiration. You can talk to Veronica in the Guild that day and ask to extend your lease so that you can continue renting the field.
Don't Lose Your Crops
If your lease on a rental field expires and you don't renew it, all of your crops in that field will disappear. You should either harvest everything before your lease expires, or talk to Veronica to extend your lease.
Give Up Fields to Gain Reputation
One of your rivals (i.e. Eda, Fritz, Giorgio, Elise) might ask you to let them use a field that you have rented. If you agree, you will gain 100 Reputation Points with that rival. Reputation Points are necessary to see your rivals' storyline events. In addition, you need to see all of Elise's rivalry events if you wish to marry her.