Can you identify the source of the leak? If it's a nail or screw that is still embedded in the tire, just repair it with the plug method described above. If you can't find the cause, it can be repaired with a patch affixed to the inside of the tire. That method will cost a few more dollars since additional work is involved.
Describe the leak and the cause of the leak and we should be able to point you in the correct direction quickly.
~ Blue Jays ~