To change extension settings on Tableau Server or Online you need to be a Tableau Server or Site admin.
Go to Settings -> Extensions on Tableau Server or Online.
Find the ‘Enable specific Extensions‘ part in the bottom.
You will need to input the exact URL of the extension you are using.
The Tableau documentation is suggesting to copy it from the popup but that is not possible.
So you need to find it in the .trex file you downloaded either from a partner (e.g. AppsforTableau) or from the Tableau Gallery.
Open the .trex file with your favorite text editor and find the following part:
Copy the url between the url tags and remember it.
Go to Settings -> Extensions again and click on
Paste your copied URL in the empty box and configure it as you like.
You can enable/disable full data access and you can show/hide user prompts.
When you are done, hit Save and your users won’t experience the popup anymore!