Well the simplest scenario would be finding studs spaced 16" apart (center-to-center) where you want the box. Cut a hole in the drywall horizontally stud to stud and the appropriate height; insert safe and screw in supplied lag bolts from inside the safe. Hang picture.
Make sure that there is no switch box for an overhead light sharing the desire wall cavity as there will be Romex stapled to one of the studs and thus making insertion of the safe impossible.
Now, my installation is more involved as there are no studs with the desired spacing in the location that I want to do the install. Thus, I am going to pul the existing drywall off, re-stud, etc.
Does that help?
Sawdust