Things You'll Need
Instructions
Right-click the Riku archive file and click "Extract to." Select the "Char" directory in your "Mugen" folder.
Right-click the "System.def" file and open it in WordPad.
Scroll down until you see "[Characters]."
Enter the following text:
"kfm, stages/kfm.def
Riku"
This will allow Riku to be selected in the Kfm stage. Repeat this process for as many stages as you would like.