there are lots of posts on this list how to do this. I haven't needed to "jump" anything. It's like filling a tire with air. In my 96 850 Turbo there is a valve--looks like a tire valve up near the passenger side fender. It says 6N or something on it. Buy a 134 recharge kit at any parts store, check the pressure (it will be under 25lbs), then hook up the can of 134 with the engine running and the AC on. It will suck that new 134 in--mine takes about 45 minute to suck a can in. Check the pressure again. You don't want it over 40ish.

I have an indoor/outdoor thermometer that I use to check the temp of the air coming out of the vents. When it gets in the 40's I know the Freon is in and working. Resign yourself to repeat this every few months if you're luck and every few weeks if you are like me (and most of us). Costs about $5.24 per can.