load on multiple areas

How can I apply a distributed load on a large area of a part,which was created by multiple extrusions. Let's say 3 extrudedsolid next to each other... and I want to put a load on top ofthem. When I setup the force, I click on 3 Faces, but it appliesload on the edges... it is not right. I want the load on one bigface instead of 3...
Any help appriciated.SolidworksSimulation