Day 3 begins with you searching for boards to cover up the broken window in your watchtower. Simply walk around the base of your tower to find three boards resting against the structure. Pick them up and bring them back upstairs. Board up the window as you chat with Delilah.
At some point, Delilah will ask you if you're ready to get to work, and you can either say yes or tell her you want to hike around a bit first. This is a good chance to go investigate any notes or Easter eggs you might have missed previously.
Whenever you say you're ready to work, Day 3 ends.