How do I upgrade my space?

I bought the personal license and got my license key but when I try to upgrade to the +25 GB package it keeps giving me this error:
A TeamDrive Personal or Professional client is required to expand the storage.
I don't get it, I already paid for the personal version. Am I missing a step? I really want to synchronize all these files as soon as possible. Thanks.
A TeamDrive Personal or Professional client is required to expand the storage.
I don't get it, I already paid for the personal version. Am I missing a step? I really want to synchronize all these files as soon as possible. Thanks.