Screw the hoses hand-tight to the cooler (some pipes have built-in screws, others a screw-on adapter). Support the stubs on the cooler with a spanner while you do up the hose union. Do not overtighten the nuts or you may risk damage to the union threads. Again, tie the hoses up with the plastic ties.
The oil in your engine needs to be kept at an optimum temperature so it can still carry heat...