You have 2 options:
The easy way (beginners), use the fat32-loader.
Read the topic about the fat32-loader for instructions.
For using ATR, you must include the OSB and MATH roms in the root.
Plus:
The ATR needs to be friendly with the OS in RAM.
One ATR can be loaded and are read-only.
viewtopic.php?f=17&t=1330The hard way (advanced), use MyBIOS.
Read the topic about the latest MyBIOS for instructions/manual.
Image-space is indeed the place to put your ATR's.
You need to partition the card with MyBIOS, then use the PC-tool to put ATR's on it.
Plus:
The ATR needs to be friendly with the MyBIOS in RAM.
Eight ATR are accessible (in a row) and R/W
viewtopic.php?f=17&t=1310You are browsing the older hardware with IDE-port.