I have Macbook 12 with El Capitan. By mistake I used my icloud email when I set up the App Store on it. Now I realized that some apps I paid for on IOS are same on MacOS and would like to use my IOS App Store id on them. When I try to enter this ID on Macbook App Store it gives me error. What are my options? I would like to avoid erasing my Mac. But if erasing and restoring from back up will do the trick I can do it. Thanks!