Use the BIM exchange button on the environments tab.
I can't remember if you can do it from 2012. You can certainly do it from 2013 and 2014.
Typically the workflow is:
And that's about it. 2014 is better for this workflow because there are some nice simplification tools, but I'm fairly sure it works OK from 2012.
(Just remembered: For ADSK you don't need to simplify in the Part file - that's just for .RFA files which can only be created from 2014.)