How to change APK sign?

I’m tying to upload my android game to test in-App purchase,but after upload completes it gives error as follow,
“You uploaded an APK that was signed in debug mode. You need to sign your APK in release mode”.

Any help would be appreciated.

Thanks in Advance

Export it to eclipse and sign it from there. Eclipse can do the whole process for you very simply. There is a very straightforward how-to on Google Developer, Page 1. Or 2.

Complete the Type-A-Number challenge tutorial for a full run-through.