You add your MAME roms like anything else. When the importer asks for a platform put Arcade if you already added MAME as an emulator the next form will be populated with MAME (if you set it as your default arcade platform) if you haven't added it yet then click add and point it toward your MAME.exe. When asked if you want to copy, move or use ROMs in there present folder for MAME you are best to leave them where they are and if you do choose to move your games remember to point your .ini to the appropriate LaunchBox folder or MAME won't find your games. As you go through the wizard there will be a special form that is only for MAME that will alllow you to choose to not add non-working, clones, bootlegs and hacks along with a few other options. Complete the wizard and wait. I was waiting over like 15 hours for it to finish today on my kitchen HTPC and then our electricity went out due to the weather so now I may have to start the whole process over again from scratch.