Need a "NUDGE" over the top?

I am working on my first (extensive) skin, in PS, and while trying to change font size for my track and time (info), I can't seem to figure out where and how to enter the correct command? I know that it's: fs(x) but do I enter: ex. fs(24) inside the ( )'s and where in my layer stack, (above Track, and also Time)? Forgive me for being so Retarded but this is REALLY my first attempt at Skinning, even though it's so easy with PS. I guess I just have to get used to the way things are "built"!!
Thanks in Advance, all!
Thanks in Advance, all!