It depends on what you want and how much ram you've got.. Mounting an 880K RAD disk on an 1MB Amiga.. Should work..
Anyway. If you're running amiga OS 1.x (1.2 or 1.3) you need to open op a CLI or shell and type "mount rad:" and a disk should appear on the workbench.. You'll need to edit the mountlist to create a 880k RAD disk.. I'll need to dig it up if nobody else has a mountlist ready..
If you're running Amiga OS 2.x or 3.x you'll still need to edit the mountlist, but you can start it much easier as described before in this thread..
Then you'd need to find some ADF disk utility to write the ADF to RAD, but still, I doubt you'll can edit the disk..
Maybe you can say what game you want to edit (Or did you allready say ? Can't remember...)