[Plugin: Random File] How to Install

Hi,
I realize you have instructions for installation, but the information is above my knowledge level. Could you help me with a step-by-step?

After I activate the plugin, what comes next? If I am reading this correctly, I am supposed to copy one of the two codes provided into my theme php file?

This worries me, as I never am successful in adding code to my php file — every plug in that instructs me to copy code into the php file, I end up with a blank website and have to restore it.

Can you help me understand exactly what code I need to paste and WHERE I need to paste this in my theme php file?
Thanks!

http://wordpress.org/extend/plugins/random-file/