whenever i create an acct, it doesnt give me the option to make a username

[Bluu501]

So basically, i made an account a while back and it had me put in my email and password which i did and verified the acct and all of that but whenever i go to the launcher to login it says to put in my user and pass but it did not give me an option to make a username so i just put in my email and that just says invalid user or pass so i have no idea what to do for the user.