In this section of the guide to Mr Prepper you will learn how to acquire the revolver - the first firearm.
The revolver is the first gun in Mr Prepper. You will receive it from Bob from the Mine when you bring him glasses from Jenny during a story mission. The gun is broken - take it to Joe from the Junkyard, and he will be able to fix it. In return, however, you must provide him with a piece of aluminum foil - only then will he give you the fixed gun.
You can also buy ammo from Joe later. You will find the foil on your first trip to the desert. The revolver requires ammo to work; one clip can hold 6 rounds - remember to reload it.