Telling a magazine from a journal is not always simple. When your instructor specifies the use of a journal resource, review the two-page guide found at the following link to help you choose:
Keep your initial search simple--set the limit for "Full Text" first, but save other limits (such as date ranges, number of pages, peer-reviewed, etc.) until you see the results list.
Look for common database tools (suggested subject headings, abstracts, citation help, emailing and save options) on the edges of the page, often in a color bar above the search boxes or in a separate frame on the right or left of your results list.
There are many periodical titles available in ProQuest related to religion. You can search for them in the databases by looking at "Publications". The titles listed here may or may not be strictly American in scope; some have international subjects as well.