To "dispose of" something means to get rid of it. It can mean throwing something away in the trash:
All employees must learn the proper way to dispose of hazardous medical waste.
The nuclear industry has not found a way to dispose of radioactive waste and protect power plants from terrorist attacks.
Sometimes, like in the example at top, you can use the phrase "dispose of ___" as an indirect way to talk about killing something.
It can also mean getting rid of a dead body. For example, a gangster character in a crime film might say:
Is there a furnace where we can dispose of the body?