Hello.
I have just seen your MP :-)
So you have an Ateobus but your are not a french amiga user?
You need to plug the P8 and P9 AT connector on the white connector. This must be done so the BLACK WIRES are all in the middle and not on the border, be careful!
The blue wire must be plugged on a small pin connector next to the white connector. However, the whole thing shouldwork without this wire, as it is only needed for -12v.
Don't forget you need too to power the motherboard through the floppy power connector.
About mounting the bus in the tower, it is made for the Ateo Tower 1200 (it has vertical backplates). In order to use another tower kit, you have to do some hacking yourself.
Be sure to install all the hardware correctly before bothering to install any ateo software, as strangest things might happen then :-D