Steel compression gaskets go on dry. Lube the o-ring with some refrigerant oil. Depending on what type of refrigerant you use, will dictate the oil.

Mineral based oil for R-12, and the PAG oil for the R-134A if that's what you are using.

Pressure test when you are all done at least 150PSIG. The compressor gaskets can be leak-prone at suction and discharge connection points. Then evacuate to at least 1,000 micron level before charging.