Welcome to ArchiCAD osue07! I first learned how to work with the curtain wall tool in ArchiCAD version 12 last year despite being a user for 5-6 years. What really helped me understand all the functions was this particular tutorial available for download
here. You will get a good grip of it by the time you are halfway through all the chapters. Hope this will help you also.
As for modifying the height of the curtain walls, I've been a huge fan of offsetting the scheme edges in 3D edit mode. You turn off the frame and panel views and turn on the scheme view. That part is covered in one of the earlier chapters of the tutorial I linked.