How to use F1, F2, F3 and F4...

I cannot use F1,2,3 or 4 with my new character! I have a Ranger who can use F1 for an attack bow and F2 for lets say a foci bow.

With my new Warrior I cannot figure out how to get it working!

Please help me

1. Press I to open inventory.

2. Above your backpack icon, click Weapon Sets.

3. Enable whichever ones you want.

Thank you. I need this because I have a Vampiric Axe of Fortitude and I need to be able do put it away fast