This is the post I made at the time:
http://www.atari-forum.com/viewtopic.php?f=117&t=34710&p=380109#p380109
Never got a reply and there was loads happening with the RS-97 and other software emulation based devices so I just got drawn away from the device. I've ordered a 128mb ram module so when it arrives I'll go back and update everything and give it another go.
The forum is not very helpful for newbies. I was confused about the main mister, menu and console cores. They need to be in sync. This is why I setup the update script and everything is now automatically updated (I use a filter to only check updates for the installed cores). Anyways, let me know how it goes.
Regarding your questions.
When the device boots, you have 2 main menus:1. "System Settings" for system joystick/keyboard mapping and scripts
2. "Cores" to start your installed cores
Use the menu key (in my case L+R) to switch between them.
When you start a core, you have 2 core menus (press the menu key):1. The core menu to load ROMs and configure your core, e.g. Neo Geo
2. The "System" menu to start a new core, define core specific buttons, reboot and more
Use the left / right joystick buttons to switch between them.
Now if you want to go back to the main boot menu, just do a soft reboot in the core "System" menu.
PS: The black screen you mentioned is probably what you get when starting a new core. Some cores display the core menu, while others start just with a blank screen. In this case, just press the menu button. This is a bit inconsistent, all cores should display the menu at startup.