Although there could exist differences in concept for hull design between your CAD program and Delftship, the techniques are enough similar for you to use Delftship 3.20 free version easily. You can download Delftship and one of the many example design files, and use them as a base for your own design.
It will be of course fair to give credit to the author of the design if you use it (e.g. based on Delftship Design 249). You will first need to register yourself to get access to the download sections and the forum.
There is also a manual as helpfile, a tutorial, a forum and enough resources to finally export the design to your 3D program. If you cannot import DXF 3D meshes, you will have to resort to unhandy offsets and textfiles, but it will not be the end of the world, and you will have a nice hullform, with correct hydrostatics and realistic water resistance values, anyway in a correct order of magnitude.
Optimizing the underwater part will not be necessary, but try to look at photographs of similar hulls and to keep your design as close as possible to the model you have chosen, the size being less important than the proportions.
Good luck,
Luc
