If it was me you asked then I use the following thread’s last 2 posts to start AppImage. GUI packages X11 missing? - #4 by StefanH
Or Add Linux Applications to Launcher by Creating .desktop File - Technastic
This is to create an “executable” icon to launch AppImage from under the launcher.
To make AppImage executable I usually just right-click the file and select properties, rights and click in the box at the bottom “allow running the file as a program” (translated from my native language).