I recently became certified in this area. There are a lot of free CEU's on line....I used places like Gannett Education online, Medscape LLC, and Nursing Spectrum Continuing Ed. Looking at my application to take the exam, some of the course titles I have in my records are: Knocking Out Pain Safely with PCA, Recognizing Drug Seeking Behavior, Identifying Pain in the Hospice Patient, Complex Regional Pain Syndrome, Type !,Common Fallacies About Cancer Pain. You can also use conferences you have attended if they apply.
Check out the references for the test and order some of the texts to study from. I studied on my own, looking at all the specific test content/objectives......I gathered this information. There are some good practice tests on the ASPMN site when you are nearly ready to take the exam. Give yourself a good 4-6 months to study the material and work on the practice tests. There is a LOT of information to cover but it is fun to learn about it!