From the picture, look like you strip the GPU. You need to put back the radiator. You strip the GPU only if you immerse it in 3M Novek fluid.
For mineral oil and other fluid except 3M Novek you put the hole GPU assembly (Without fans or whit them depends of your choice and cooling) and make a circulating cooling system for the mineral oil.
3M Novek is a different story altogether you can research it, but the setup cost are very high.

Hope it helps