How to "assemble" a model from part files

 From:  Jimmybuckets
8113.1 
Hi Guys,
Just wondering if there is an easier way to assemble a model from part files. For example if I want to put a bearing in a wheel and then put that wheel on a bolt and so on...
I have had some success, but it take a lot of time to put the parts together and know they are correctly orientated. Hope this makes sense. Maybe MOI is the wrong software for doing things like I am trying to do, but it looks like there are a lot of people using it to make very complex models.
Thanks!
Erik