He obviously made a shortcut to the folder.
make sure the target string points to your soldat.exe with -mod "mod folder" on the end.
For instance, if you were trying to play my mod
your target would read as:
"C:\Program Files\Soldat\Soldat.exe" -mod "Soldat Enhanced"
Or to be less specific:
"<Soldat directory>\Soldat.exe" -mod "<name of the mod folder in mods\>"