Complex sentence: After Ultron is defeated, Pym rejoins the Avengers and feels want to spent with them once again by letting himself to be sealed on DISK like his teammates does, and creates Jocasta.
Split into simpler sentences: After Ultron is defeated, Pym rejoins the Avengers because he feels like he wants to be with them again. He lets himself to be sealed in a DISK like his teammates, and creates Jocasta.