How to select elements enclosed by a solid?

Hello. 

I have this large model that is already meshed with surface elements and does not have any geometry associations. My goal was to select elements along strips of a certain width, along the length of the model.

I created a solid body in a CAD program for my required shape (with enough tolerance on both sides) and imported it into HyperMesh. It is now superimposed upon the elements, as I intended it to.

My goal is to select the elements (or even the nodes) enclosed by that solid body. I tried to do that by using the "by Geoms > Solid" option, but I understand the elements/nodes have to be associated to the body for that to work.

How can I associate them to the newly imported body?