Run a good size braided wire from good power
source like the battery and run it to pump location.
Put your relay somewhere near pump but in a place where you can access the relay for servicing.
Connect power source to relay. Run per from relay
to pump. Run switch wire from relay to trigger
Location. This could be your fuse panel. Somewhere
Where you want the pump turned on.
Follow pump instructions. Probably need fuse(s)