You will need to have the condenser replaced if the leak is from the condenser. Be sure to check for other leaks using a dye to make sure that's what needs replacing. After the problem is corrected be sure to have the system purged of all air before adding new freon.
This must be taken to a repair shop because of the chemicals found inside AC condenser units, law requires it to be handled by a trained professional and disposed of.
You are going to want to find out where the leak is coming from. If you can find it, usually a hose, you can take it off and go to your local appliance store and they will give you a replacement.
You need to take it into the shop they have machines they can put on it and it will tell them exactly whats wrong with it and they will be able to fix it right there you need a license to fix it.