
1) Having unplugged the MegaSTe, remove the 68000 CPU chip (using a dedicated PLCC removal tool or a tiny screwdriver as I did, gently prying into the two long slots to wedge it loose -see photo below)
2) insert the 68000 into the MonSTer board, taking care of the direction (there's a 45 degree corner on the CPU chip which should match the socket -see photo below)
3) insert the MonSTer board's white socket carefully into the (now empty) CPU socket inside the MegaSTe. Take care to ensure the orientation is correct! That's how far I got today, so I powered on the computer and it booted up! No smoke or other irregularities, so I must have done something right

But I'm a little puzzled, because according to what I've read here I should enable the FLASHON jumper in order to use the original TOS ROMs (or was it the other way round?). In any case there are no jumpers at all on my MonSTer board, and I can't seem to locate that particular one either (perhaps it's one of those unmarked jumpers?).
So next is the DMA interrupt cable which came with the board. Looking up where pin 10 of the ACSI connector was I used a multimeter to see if there was somewhere on the motherboard I could attach the wire and I found it to be at the end of R419 (see photo). When it's all been tested I'll solder a wire here for a more permanent, failsafe connection. The other end of the DMA interrupt request cable goes somewhere on the MonSTer board, but where? To me it seems it's one of the two pins marked ACSI (both pins work -why are there two by the way?): So does it all look good so far?