Upgrading your Spotify account to Family isn't a difficult process, but it's not immediately apparent where you need to go to make the change. Even worse, you can't make any of these changes from within the mobile or desktop Spotify apps. It all has to be done in a Web browser.
If you're an existing Spotify Premium or a free user, the process for upgrading to Spotify Family is the same.
First, navigate tospotify.comfrom your browser and login to your existing account or create a new one.
Next, go tospotify.com/family. Alternatively, you can click the arrow button beside your username to reveal the dropdown menu and clickAccount. From the account overview page, clickPremium for Familyin the left sidebar.
Enter your payment information and clickStart my Spotify Premium.
Invite up to five other people to your Spotify Family account using the email addresses they use for Spotify.
Thanks for the answer. maybe I have not been so specific. I have the premium subscription that is already paid until October / 2018. Can I use this "credit" and turn my premium account into a family account?