Use the credentials you received (directly or via an external website) and log into the account.
Make sure that the content on the account is correct (valid for the advertised period, correct subscription plan) and that it is NOT a part of Spotify Family Plan (here).
Change the credentials to make the account your own:
Change the email
Change the password
Add 2FA
Warranty Information
Full warranty offered! We guarantee a working product, or your money back!