You cannot change your Slixa ID or Slixa profile URL directly. However, changing your stage name will automatically change your Slixa ID and Slixa profile URL. To change your Slixa stage name, login to your Profile Editor and input your new stage name in the appropriate field. Be sure to click the blue "Save" button at the bottom of the page so your changes take effect.
The direct link to your Profile Editor (Profile tab at the top of your dashboard) is: