The trap is filled with yellowjackets. I want to dispose of it, but, am unclear as to how to "close the trap"? Any suggestions?

If yellowjackets are still alive in the trap, wait until they have expired before disposing of the trap. When you take the trap down, the yellow top can move down into the bag. The closure isn't water tight, so it's best to keep the trap upright while moving it to the trash.