More accurately, you can import a solid file, eg iges, but it has no physical meaning, it is just a graphical entity that gets attached to a pre-existing part.
Amazingly enough the command (in View) is File Import.
Bear in mind that if you do this ADAMS does not have solid part 1 hitting solid part 2, it has a marker on part 1 which has a defined relationship with a marker on part 2. If you want to have parts hitting each other then you have to model the parts themselves in ADAMS from primitive shapes, and then tell them that they can collide with each other. The modelling step is easier said than done for complex parts. Your execution time will increase drastically.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.