Merging volumes - what to do after landmark registration

I wanted to integrate one volume into another one (at a certain position: That is why I was using Landmark registration to align both volumes. It also worked as far as I know. But now I have the problem that When I want to segment the ‘transformed outcome volume’ I can´t see an integration of the first into the second… Am I using the wrong tool for integration at a certain position?
Thanks for your help!

What did you see? Can you post a screenshot before and after registration? Have you applied the computed transform to the volume? (you can apply a transform using Transforms module; or in Data module’s Transform hierarchy tab, drag-and-drop volume under the transform)

You can find several registration tutorials that use Fiducial registration wizard module, among SlicerIGT tutorials.