Assembly Analysis of Two Aluminum Extrusions

Where are you stuck?

My suggestion is to start simple. Make your 2 extrusions just blocks to start. Fix the holes, apply the appropriate end conditions on extrusion 1 and maybe 2 (no detail provided for either). Apply a load and run it with solids.

Then move on to the appropriate idealizations. Shells for the bracket first and the appropriate contacts. And then investigate beams for the extrusions. Then swap the extrusions for the final shapes and you'll be done!

On bonding, check out the mixed mesh tutorials.

Remember that fixing and bonding are generally different. The latter is contact the former a restraint. Without the restraint, it flies off into space. Without the contact, the parts don't stay together. When you are first starting, I always suggest adding fake restraints, excluding all parts except for one and using the gravity load. Add parts one at a time so if there is a problem, it is easy to identify.

On mates, see Jerry's response and what I've written above. The mates just develop the relative locations, the contacts, restraints and connectors do the rest.

On interferences, yep, you need to get rid of those. Overlap is only allowed for shrink fit. The maximum amount of interference should be when you have treat coincidence as interference. That will show you where global contact will apply.