To use ClipGlider, you need to perform these steps just once: turn it on in Safari extensions Settings and allow it on all websites (same is necessary for any Safari extension).
Here is how to do that:

You can turn on ClipGlider extension in Safari Extensions preferences.

ClipGlider extension is currently on. You can turn it off in Safari Extensions preferences.

ClipGlider extension is currently off. You can turn it on in Safari Extensions preferences.