Periodicals (magazines, newspapers, academic journals) contain short articles on a very specific topic and often present the most current scholarship on any given issue.
To find articles, you will search in an online database. Databases can cover a wide range of academic disicplines, or can be very specific. For research in an area like evangelism, it's best to use a subject-specific database, like ATLA Religion, which focuses on theological journals.
Note: In these searches, I used quotation marks to get to the most relevant articles, since the exact phrase must appear in the search results. Identifying and using only essential keywords, as opposed to typing in your exact research question, helps return more appropriate articles.