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?