To run the Nano emulator at least the Nano system ROM files should be specified in the 'ROM' field. Default Nano ROM location is the Nano directory (located in the application data directory, see Directory and File Structure) and the default filename is 'nano.rom'. To change the location use the 'ROM' button to browse for the file, do the same to change the filename or type in a new file name in the text field.
The binary, Intel hex and RCS Elf Emulator hex format are supported.