How do I find research that shows if twelve-step programs are effective for substance abuse treatment?

A great place to start is the Search All Resources box in the middle of the library's webpage.  

Type in twelve step programs substance effectiveness and click Search.

On the results page, go to the left side of the screen to see all the limit and filter options.  Click in the box next to Peer Reviewed. That will narrow your search results to articles from scholarly, peer-reviewed journals.