do a search, there was a recent discussion about this.
Also, check out Graphisoft's
instructions here.
Please add your platform and AC version to your signature.
Erika
Architect, Consultant
MacBook Pro Retina, 15-inch Yosemite 2.8 GHz Intel Core i7 16 GB 1600 MHz DDR3
Mac OSX 10.11.1
AC5-18
Onuma System
"Implementing Successful Building Information Modeling"