This thread should help you with the basics of CAD:
This thread that should help you get up to speed on iMates:
You can simply search the forum for a plethora of Inventor part libraries. Locate one that has iMates already added to the parts in the library, and use it.
Side note: If you wish to use Solidworks since you already have it, there are actually a few VEX libraries available. I have no idea about their quality though.