Which pre-installed OS are you using? AmigaSYS with UAE/3.9? I see Amistart on aminet, so you might want to go there, download it and read the docs. If you look at some of the other working menu entries, this should help you to see how it works. I'm not familiar with Amistart, but usually with menu launchers you can have them run programs as if you had doubke-clicked on them (WB mode), or as a CLI command. If you were to use the CLI mode then you'd want to use the command c:whdload to run your mygame.slave file where 'mygame.slave' would be the full path to your particular whdload.slave file (game).
c:whdload
