Mark, you must :
1. repair the leak.
2. pull a vacuum on the system for at least 30 minutes to remove any moisture ( 2 hours is my choice )
3. feed in the proper amount of R134A ALONG WITH the recommended quantity of 'PAG' oil. ( with the compressor running )
( Usually, one of the R134 cans is one marked "with PAG oil" or "with compressor oil" )