You cannot load curtain walls only curtain panels and mullions for use in curtain walls. Curtain walls are a system hosted element. Curtain walls have mullions based on mullion family profiles and curtain wall panels family that can be made up of solid form or void modeling and/or symbolic linework. Use the HELP menu and tutorials to learn how to work with Curtain walls and the families associated with curtain walls.
Mel Persin, AIA
AEC Technology Consultant
Technology to Visualize and Realize Solutions
MasterGraphics, Inc.