Utilize Internet search engines. Type the words "Christian literary agents" in the search field. You'll get numerous results, complete with submission guidelines and contact information.
Visit your local bookstore or library and purchase or check out books that provide listings of Christian literary agents. There are numerous books listing literary agents in various categories. In particular, Sally Stuart's "Christian Writers' Market Guide" is updated annually. Writer's Digest's "A Guide to Literary Agents" also publishes yearly and contains a category for Christian literary agents.
Join a local writing group. Find a writing group in your area and meet with other writers on a regular basis. Fellow writers tend to share information in the industry with each other.
Attend a Christian writers convention. Converse with other Christian writers and publishers about your book. Pitch your book to agents at these conventions. There are a number of these events held every year in various cities. One of the more popular ones is the Christian Book Expo.