If you acquire a new weapon, you can easily choose which Weapon Slot to assign it to by pressing Equip. However, if weapons are in a slot already, you'll need to do the following: 1. Unequip the weapons you plan to place in a new slot. 2. Re-equip the weapon. 3. Assign the weapon to a new slot. Quickly swap weapons by holding L1 (PS4/PS5). Use the Right-Stick to select one.