You use the radio maintenance tools to edit the feature string, once a new string has been assigned to your radio after you've contacted a dealer that will work with you on this.
If you do not know how to use radio maintenance tools to edit the feature string, then I STRONGLY suggest that you send your radio in to them and have them handle it, and while they're at it, they will update your firmware and DSP code and check and align the radio. This is worth doing.
I do not recommend attempting these things yourself if you have not been taught to do it. Disaster lurks on "do it yourself" path if you haven't received a good education on this and/or you don't have the necessary equipment to align the radio.
It's really not something you should try at home. Really.