Air conditioning compressor oil

I have a 94 S-10 2.2 with air..I had to replace the AC compressor. One guy tells me to add oil into a drain plug on the side of the compressor, but I have heard it needs to go in at the orifice tube? On the back, half in one port half in another? Does anyone know the correct procedure? I know the amount I just don't know where to put it!
Thanks

I was always told the oil drain plug, but since you have to get the system charged at a specialist, and they waht to do the job why not just get them to fill the oil.

I really can't imagine it taking them more than a moment to fill it

The system isn't going to be charged, it doesn't work, hasn't for years. The bearing went bad in the pulley and had to replace the whole thing...When I did it today, it started squealing again, I thought I may have put the oil in the wrong place...It appears the new one is bad also.

Why not just go to the autowreck, and buy a bracket that wasn't made for air conditioning. Then you can eliminate the weak link, and get the money back from the compressor.

what a pain in the butt... getting a bad part

You mean just buy a pulley? I guess I couldn't just get a belt for a truck without ac and reroute it, I thought about that, but I guess there is a pulley there.

The system isn't going to be charged, it doesn't work, hasn't for years. The bearing went bad in the pulley and had to replace the whole thing...When I did it today, it started squealing again, I thought I may have put the oil in the wrong place...It appears the new one is bad also.

The oil in the compressor doesn't do anything unless the electric clutch is engaged which from your posts, apparently it is not. If you have squealling it is from the bearing in the electric clutch and can be changed without disassembling the compressor.

Thanks to all..I replaced the AC compressor, still had alot of noise..replaced the tensioner pulley and put in a new belt..all OK now