ive recently acquire a stellaDC disc that goes into my Dreamcast, ive been able to use the roms that come on that same disc by using the method of holding down the start button when the main screen comes on,then i scroll and find the rom i want to use

but it says on the screen to insert disc of roms??????? does that mean i can put "my own "roms on a disc and test the roms i want to ??????? if so and how ? "swap method"
thankyou in advance
eric