This mod is not really for custom theme. It is mainly for SMF default theme or its similar variants. If you wanna build your forum from SMF default theme to look like FB, then may be I can help. But not from custom theme even if the custom theme is created by me myself.
But I'd suggest, create a topic in Coding Discussion board or Graphic and Template board on "How To Turn My Forum To Look Like Facebook?".
Using this mod on default theme is as simple as installing it, then your menu is fixed at the top. You might to do some minor adjustment to its css to move it from left to right. Add this code to your default theme index.css file:
#menu_nav
{
float: right;
}
With this, you will have your menu to the right. IMO, this code will work on any theme including Face1 theme as well but without changing its current menu to top.