DXF and Netlist
Not sure how complex this board is. Hopefully not very for this situation... You will not be able to associate a netlist to the DXF file. It is most likely just lines, polygons, and arcs with no part information included. I take it you are using Orcad layout 9.1 for this endeavor? I have very little experience with this tool so I will not be of much help there. But I am certain you can import dxf files and create board outline from that data. You might want to import the dxf then delete all data except board outline, then create board outline. Repeat as necessary.
There are some tools out there that would make this task easier.
1. Autocad
2. Cam350 (with this tool you could import dxf, create board outline, create layer stackup, create padstacks, create parts, import netlist from Orcad, and even export layout to Orcad)
The above process is time comsuming and tedious it would most likely be better for you to take dxf into your layout tool and place parts accordingly using dxf as a visual template.
Eda