Measure and cut the copper pipe to the appropriate length needed to connect to the AC compressor.
Sand about two inches of the end of the copper pipe and inside the connector. Sand until you can see the new, shiny copper metal.
Apply flux to the end of the copper pipe and to the inside of the connector. Apply an even coat around the outside end of the pipe and the inside wall of the connector. Slide the connector onto the end of the pipe.
Turn the flow of propane to the "On" position on the torch and light the flame with the lighter. Heat the pipe and connector with the flame until you see the flux bubble. Apply the solder to the opposite side of the pipe where the flame is, and the heat from the flame and pipe will draw or suck the solder into the connection, sealing it. Move the solder around the pipe as you heat it, ensuring the solder is all the way around the pipe's connection. Wipe off any excess solder with the emery cloth.
Turn the flow of propane off to the torch to extinguish the flame, and allow the pipe and connector to cool. Repeat the above steps to solder any additional copper joints.