Help with Demul needed.

[1peterkim123]

So I got pretty good hardware(In attachments)
I've tested out on nullDC before;
Was trying to play JoJo's bizarre adventure, ran over 100 fps and had to limit in order to play.
Now it just kinda lags about when I start dreamcast.

Also, I don't know how to emulate .iso files with this emulator.
So if anyone could help me, that'd be great. (Also, it's the PAL verison of JoJo's Bizarre adventure)
/watch?v=UWfIKWW3ZRA
Youtube link to video.

EDIT;
I've somewhat made it so it can go up to 60fps, and I've figured out how to mount the image, but I can't seem to get the sound to work properly.