Make sure you are in the Home menu. Navigate to the Settings menu, and choose Restore Default Settings.
As a reminder, a list appears, stating that all the settings that are going to be restored if you proceed. There are no options by this method of restoring only some of the settings. Navigate to the bottom of the list, and click the X to continue.
PS3 system restoration brings the system back to the way it was when you purchased it. You must go through setup as if it were your first time.