BIMx models
Click the grey “down”arrow beside the files at the bottom of the page
The software for PC or Mac can be downloaded at Graphisoft
http://www.graphisoft.com/downloads/bimx/bimx_desktop.html
there is a pdf reference card there which can be downloaded too
or when the software is running press esc to get to the menu
then press “controls” to see the commands
repress esc to get back to fly mode
For a iPad, search for the free BIMx software at the Apps Store