You can find the link to your account management page from the "Thanks a lot for your purchase" email that was sent to your payer email.
You can also locate the link in Team Management, under the Billing tab. If you select an invoice, you should then see the link in red to the right.
For Data Studio users, there is also the Team Management tool that you can use to do some license management from. For more information, see Team Management Overview. (Note that you still must change payer details and renew in Account Management. These are not available in Team Management yet.)