Recharging a/c in 90 240 no trubo. I understand it is easy and cheap but can't figure out how to do it.

 

Turn the car on, put on the A/C and turn the fan all the way up.
Open the hood and find the Accumulator/Drier, right next to it should be the low pressure charging port.'
Connect your gauge (I like the cans of refrigerant with an attached gauge) to this low pressure port.
Dispense the refrigerant with the can it the upright position.
You generally don't want to get above 30 PSI.

 

That photo looks like the engine bay of a late 92 or 93 because it is factory R134...Not all 240's have the canister refill port in the engine compartment like the later models do...If that's the case you need to refill from under car on the a/c compressor itself or if you can from top but unless you have done it before it's difficult to get to. Make sure you fill on the low pressure side which is the nipple furthest to your left if under car and looking at back of compressor. You will need to get a retro fit kit for R134 because your car is R12. It should come with the fitting you need, oil, and R134 refridgerent but make sure to buy extra R134 because they usually do not give you enough...so other than location of where the process described above is accurate...make sure you get a filler with a gauge(system has a capacity of 3.5lbs) on it so you can tell when the system is filled or if it cannot be filled and some component is bad...Good luck(hopefully it's on top because it gets hot under the car )