location for the AC to recharge

I have a 2000 Mercury Cougar V6 and I
just can't locate the AC plug to
recharge it up.. i see 2 black knobs but
it doesn't have the H or L so im like
clue less about this..  im learning about
my car. I jst got this bad boy 5months
ago an its only got 125,000 and runs
like a champ.. I turn the AC on full-blast
and let it sit there until it warmed up
and the compressor kicks on it just
stopped blowing cold air it was fine
when I first got the car.  So u jnow its
not tha.  So if you can help me anyway
that I would really appreciate it thank
you