How can I edit showreels?

In the menu, click on "Manage Media" and then on "Showreel Manager".

On the left side, you will see an overview of the currently selected showreel. On the right side, you will see all uploaded videos (or audio files). You can drag and drop videos from the right side into the currently selected showreel on the left side.

By default, showreels in your Filmmakers profile are publicly visible. To change this, click on "Edit Showreel" and uncheck the box next to "Filmmakers Profile (publicly visible)" in the "Showreel Visibility" section.