1994 Jaguar XJ6 where do I put the AC recharge hose?

Question; Are you using R12 or the new 134A?
I am assuming you are using 134A. It is important that you add the new oil first if the system has the old R12. These instructions should come with the kit.
Anyway, to your question. The suction port (low side) will be on the hose running from the expansion valve (Aluminum block close to the fire wall) to the compressor. The fill port should be close to the expansion valve, but it might be down by the compressor Not the line running from the radiator to the compressor, this is high pressure. If you are lucky, there will be a canister close to the radiator that has a small "sight glass" in the top of it If the freon is low, with compressor running, you will see bubbles passing through the line. Slowly add freon until you don't see anymore bubbles, and your system will have enough. Sight glass is on the high pressure line. Be careful not to overfill the system. It will lockup your compressor. The compressor pumps vapor not liquid. Hope this helps.