To run the MCDS emulator at least the UT62 firmware file should be specified in the 'UT ROM' field. For full functionality also specify the Assembler & Editor ROM as 'ASM ROM' and the BASIC 3 ROM as 'BAS ROM'. Default MCDS ROM location is the MCDS directory (located in the application data directory, see Directory and File Structure) and the default filenames are 'ut62_rev2.bin', 'edit_asm.bin' and 'basic_3.bin' which are already filled in. To change the location use the 'ROM' buttons to browse for the file, do the same to change the filename or type in a new file name in the text field.
Note that files in binary format, normally using extension .bin, will be loaded at specific addresses UT ROM on hex 8000, ASM ROM on hex 9000 and BAS ROM on hex B000. Intel hex and RCS Elf emulator hex format include storage locations and as such will be loaded in the specified address location.