Click on the Domain Name that you wish to manage.
If you only have one Domain Name, you will automatically be redirected to its management page.
Click on the Hamburger Menu, then select Renew from the drop-down list.
You will be redirected to the page where you can pay for and activate your Renewal.
Note: The maximum number of years a Domain can be registered will depend on the policies set by its governing Registry. As such, NOT all Domains on Active status will be legible for Renewal. If you've reached the maximum, the Renewal will be rejected.