To specify which disk HW to use, use the 'Disk Type' choice button (green ellipse) to select, none or IDE:
To specify which .ide file to use click the 'Disk' button (yellow ellipse) or type in a specific ide filename (orange ellipse). Default 'pico.ide' is used but this can be changed to any file name. Number of tracks, heads and sectors can be specified via the Device Port button, default is 512 tracks, 4 heads and 26 sectors. ElfOs can be installed on the ide disk file. The eject button (purple ellipse) will empty the ide filename field (orange ellipse).
After initial start-up the file pico-installation.ide is made available including a pre installed Elf/Os. The installation file will be renamed to pico.ide if that file doesn't exist.