Checking for AC leak w/ Dye

Hey all: My 1994 J30 seems to have a leak somewhere in the AC system. Everytime i put a can of R-134 in the system it is usually gone in 24 hours (compressor works fine). I have a bottle of the Dye (that you put under a blacklight)....
How do I inject this Dye into the system? Do i put it in the same port that I put the freon in? Is it a difficult process??
Thanks, Scott