How to install mods to a cracked minecraft launcher?

I downloaded a minecraft launcher that was cracked, and it was for 1.7.2, and I want to install mods, but all the tutorials have it to where you need to sign in with a username and pasword. Mine has that function, but when I try it, a window pops up saying 'Java Runtime Environment 7 error'. I'd like to get instructions on how to install mods without signing in.