[kramarczyk]

Inventor is going to require you to identify the contact conditions of the solid part meshes prior to solving. If you are using bolted and glued joints with no moving interfaces you can probably get along quickly using the automagic feature. On the ribbon: Stress Analysis tab -> Contacts panel -> Automatic

This will basically glue together everything that is clost to touching. If you need something different you can go into the contacts and explicitly edit them, but that is much more time consuming. Having a constrained model would allow you to import the constraints as mesh contacts.

That's about all the help I can offer without seeing the geometery.