How can a person get a sense of humor?
You have a few options.
1. Smoke a lot of weed.
2. If you don't find what others find funny, to be funny, then explore the darker side of humor. :)
To overwhelm means to cause someone to be overcome with emotion, so that they cannot control themselves. To overwhelm with humor would be to us humor in order to cause someone to laugh uncontrollably. The implication here is that the other person is hostile, and you overwhelm them with your sense of humor.