Looks like you got sold 1/2 of a full kit. Like parts were robbed out of it, the dealer could not return it for credit missing parts, so you got stuck with it. Were there any install instructions, parts list, etc, included? "IF" not they could get themselves in serious legal trouble selling incomplete parts kits for vehicles intended for highway use. Nuff Fluff though.
Google 'Cody Hitch' as they have a good unit at a good price.
Now, if you do not need the whole thing, perhaps just the end plates would adapt what you have, to what you need.
Have installed several of their units, and I do have fabrication capabilities, but the factory units go in with no mods...
If you have a Ford, or off brand truck,?, the main support bar/rail part must reach to the outside of frame rails. Then bolt/attach to the side plate, which is then bolted to the frame rail.
Bottom line: Call Cody Hitch and buy just the side plates ("IF" they will sell them separate, due to legal issues,) and get 'em installed. Actually any competent hitch installer should be able to fab some 1/4" end plates, attach same to your 1/2 azzed setup, and you are good to go.
Not meaning to be critical w/ the 1/2 azz thing, but there are no short cuts to be taken for the safety of you, your family, and the myriad of other vehicles on the road.
Future truckers: Go high dollar with the B&W thing and others, or get a good hitch at a good price from Cody. On Google, Cody Hitch will show, but the selling dept has a diff name, but still the same thing. Just follow the link,s..
PS: Am here in So Calif should any locals need some fab work, shade tree type, in the shade of my 2 post lift...