That could mean a few things. The first thing that comes to mind is a failed oxygen sensor. That's is what you may want to start with since it is the more likly and cheaper repair. The other possibility is a failed cataltyic converter. That is an experince repair. This problem can be casued by other issues as well such as leaking fuel injector or too much fuel pressure.
To be honest, this is a very tricky code. People usually start with the O2 sensor. But that does not always fix the problem. Next they may even replace the cat, which can be quite expenve but still have the issue. If I was you, I would get a second opinion from a mechanic that has a professional scanner. You don't want to throw money on parts that don't need to be replaced.
Simply drive the car for a few days. As long as there are no other codes, the light will reset on its own. It takes about 5 or 6 driving cycles which most people will complete in about two to three days, assuming you drive the car regularly.