Hi
When I downloaded for example xarchiver.scm I first load it, then I copy its desktop file in ~/.local/share/applications/ modifiyng the Exec line in this way:
Exec=scm-load -i xarchiver; xarchiver %F; scm-load -r xarchiver
I also copied the icon in ~/.local/share/pixmaps and modified the icon lines in this way:
Icon=/home/tc/.local/share/pixmaps/xarchiver.png
X-FullPathIcon=/home/tc/.local/share/pixmaps/xarchiver.png