The CLEP fact sheets have a list of books you can use to study for each exam. Using the list check the library, used book stores, Amazon, eBay for the book - I always check the books to see if they have companion websites that have free quizzes, which seems to help me learn the subject better.
On Life Span development / Human Growth - they recommend the same book as excelsior so I also got the excelsior content guide syllabus and used that to study. You then need to check the test center and find your closest test center, usually a college, and contact them on their testing schedule and fees information on how to schedule. Then start reading, taking notes and do all of the end of chapter questions. Studygroup101 has a good study guide for life span for $10 that you can use, it has lots of quiz questions. I think the CLEP exams are really good option for alot of exams and you can save so much money that way - hope that helps bril