go to your items menu, find what you want to equip, then press x

nah dude you didn't even explain it right ignoramous, you press start equip your gun then once your gun is equipped you hold down tha R1 button then press x homie

its bad karma plus it is difficult if it is your first time playing the game.

equip gun and press r1 and press X... i beat hard mode with handgun so keep it

Pause the game and then press X on your
handgun or weapon or gun and press equip.
Then exit and hold R1 and press X to shoot!

Ok I bought mine on e-bay. It didn't come with a instruction book. And guess what. I still
knew how to shoot. God this is the most retarded question I'v ever heard of.