Http://www.sparknotes.com/lit/odyssey/section5.rhtml
I actually read two of those books and it was the magician's nephew and the yearling. I liked the magician's nephew better than the yearling.
The verb here is "had given"; this is past perfect: it's a perfect tense, because it has a past participle with the -ed ending ("given") and it's the past perfect because the auxiliary verb is the past form of "have": had.
Answer:
he trains therapists to lead humor therapy sessions