I have my starting weapon equipped, but I can't figure out how to use my bow now. If I press f, it says that I don't have a weapon to fire. I'm holding a bow and a quiver with arrows though. I assume that I need to equip it, but I can't figure out how. I also have a couple other weapons that I can use with A if they aren't in my backpack, but I'm not sure how to equip them either.
You need to wear a quiver and remove the bow from your backpack into an open hand. If you don't have an open hand, you need to put whatever you are holding into your backpack or throw/drop it.