Holes or hills ???
Place the trap between hills in the run,make sure you clean the run out either side of the trap smooth the bottom of the run.place the trap in the run and make sure it can't move about wedge it with a sod of earth if needs be then cover it with soil do not firm the soil down on top of the trap.
I have written this presuming you are using a half barrel trap??
All the best
410Phil