You'll have two connectors per rad, inlet/outlet.
Run the bottom connector of the res to the inlet of the pump. Run the pump two a connector on the top rad. Run the other rad connector to the GPU.
Run the GPU to the 120rad and finally to the upper connector on the res.
Like previously said you'll have to prime the pump before using it. IE - make sure there's water in it.
Fill the res, tip the case so the water heads to the pump. Switch on the PSU (by bridging it - please read if unsure and make sure nothing is connected to the PSU apart from the pump).
Keep the case tipped so the water heads to the pump - once the res is getting low, switch the PSU off. Top up the res. Tip the res, switch on the pump. Repeat until the water no longer drains out of the res.
You'll then need to leak test and get the air out of the system.