The account in your profile is linked to the mail that you specify when paying for the purchase. One mail — one account. If you want all the master classes you bought to be stored in one place, specify the same mail in the shopping cart before paying.
When buying the first master class or when registering yourself, you receive an email with a login and password, use them to log in to your personal account. In the future, if you buy other master classes, they will appear in the created account.