i made a minecraft account years ago, i login with the username and when i click buy the game it says i need to sign in with a email, so i made a account with the same email as the first account and when i click buy it say's the user name is taken because the first account has the user name i want, how do i use the first account to buy the game???
You have to migrate your first account to mojang.com. Create a mojang.com account with the email adress, and then press something like migrate. I can't be more specific because I've did this months ago, but it shouldn't be hard.