Make sure you are using the latest version of Yabause before anything else. Once you are sure you do begin the following easy to follow steps.
1.) Open Yabause. Now click Yabause next to the apple on the top of your screen. You'll get a drop down menu, select Preferences...
2.) You will get the following under the General tab. Bios can be left blank as you do not need a bios to play games. Check the site's compatibility list as it'll tell you IF a game requires a bios to run. If the game you want to play does need a bios, and you have a Saturn bios file, then browse to its location here.
If using an original game, have Yabause set to run Cdrom device as shown. Then enter /dev/disk1 in the field above. If you have a iPod, or some other storage device already connected to your Mac and Yabause was unable to run your game, then tray again after changing the number. e.g. /dev/disk1 will then become /dev/disk2, if that didn't work then try /dev/disk3
If using a backup such as a ISO, be sure you have set Yabause to use ISOs instead of the Cdrom device under Cdrom. Also it is best that it is not a BIN. I personally have never gotten one to work. But the second I converted them to ISO, Bingo!
Moreover if mounting CD images, be sure to set Yabause to CD mode since virtual drives are just that. An imaginary CD drive with imaginary CD inside it.
3.) Simply make sure all the settings under the Video/Sound tab look like above
4.) Want to save games, then select 32 Mbit Backup Ram under Memory.
The 32 Mbit Dram is your RAM expansion cart that Capcom & SNK games made use of. Secondly you'll need enter where you want your backup RAM to be saved. If you enter what you see in the image above, it'll create a file called Internal in a folder called Yabause in your Applications folder.
5.) Once that is all done, have your game ready. Select emulation from the top menu and select Run from the drop down menu.
I would recommend using your actual games, as it's the only sure way, unless you have other means of testing your CD images. If a game loads up as an audio CD and has an inaccurate number of tracks this actually means Yabause hasn't found your game at all. If you have followed all of these steps and plan on using a backup of a game and not the actual CD, and the game still doesn't work the backup is at fault or simply doesn't work on Yabause.