If you have a wet dry shop vac take the wet dry vac and fill the shop vac canister with a little bit of soapy water.
Then take the wet dry vac and go around to where the boxelder bugs are and suck them up into the vacuum. The boxelder bugs will drown in the soapy water and die.
You should then place some mothballs around the areas where the boxelder bugs are hanging out at and the mothballs will keep future boxelder bugs away.
Borax Powder will also kill off the boxelder bugs if you sprinkle some borax powder around the perimeter of your house or anywhere the boxelder bugs are coming into your house at.