Ah, it worked! Sorry for the delayed response, just been busy.
Basically all you need is:
1.) The burned disc.
2.) The ISO in which you used to burn the disc.
Okay, if you have those, open the Cassini Emulator and go to "Emu Tools"; from there, use the "CUE/BIN" options, they should say something like "ISO+WAVE -> CUE+ISO (####)" (NOTE: The (####) may have numbers in it, if it does, that's fine.
Just click on those options and you should see that you are required to find the ISO for the game you want to play.
I haven't found out what the first option does, but I DO KNOW that it's required to do if you want to play the game. The second option creates a specific CUE file type in which the emulator can play derived off of the ISO that you supplied.
After you do that, go to "General" and pick the drive in which your burned CD is in. Then go to "RUN CUE/BIN" and open the CUE file that Cassini made for you.
After you do that, the game SHOULD play, if it doesn't. Tweak around with the region settings. Also, if it's a Japanese game, you will need to rename your Japanese BIOS to EURO.BIN and move it to the folder in which you installed Cassini. (You can move your current BIOS someplace else if you like).