How To Migrate Your Account
1) Go to https://account.mojang.com/migrate
2) In the "E-mail" box put in the email you purchased
3) In the "Username" box put in the username of the account you purchased
4) In the "Password" box put in the password of the account you purchased
5) Navigate Under the "Details for your new Mojang account"
6) Under "E-mail" and "Repeat E-mail" put in Your email that you want your minecraft account on (Make sure you don't have a minecraft or Mojang account already registered on that email
7) Under "Date of Birth" put it any date before 1999
8) Check the "I accept the Terms and Conditions, including the Privacy Policy, and the Minecraft End User License Agreement" checkbox indicating you accept Mojang's rules
9) Click the "Migrate account" button and you now have a fully working Minecraft account.