Hello!
You can manage your Master profiles (as well as most other profiles) by clicking on the "Profiles" tab and in the box called "Manage Existing Profiles" click on the Manage Profiles link. You will then see a page with the profiles you have created, and you can sort them by clicking on the specific type of profile at the top.
To delete a profile, check the box next to it and click the blue "Delete Profile" button, or use the drop-down menu to edit or delete it that way.
Hope that helps!