From the My Studies page, click on the required study.
Click on the App Templates tab.
Find the required Template entry and click on the image / icon. (you’ll notice an Edit icon appear)
This will take you to the same builder page from when you first built your Study Template. You can also edit the title and behaviour of your Template here as well.
When you’re finished making the necessary changes, click on the Save Changes button (or Cancel if you don’t want the changes saved)