[jan-jaap]

The two CPU bricks are craylinked into a 16 CPU system. The graphics bricks are linked to the CPU bricks using XIO links.

So first you link the CPU bricks into a single system, like a single rack dual module Origin 2000. The CPU bricks might be side-by-side, one in each rack.

Then you connect the graphics modules

Honestly, I would at least browse this manual at least once. The Site Preparation Guide might be a good one too.