This flying method is a very simple example. If you were to take it further, you could imagine how to fly a person. It works the same way, but uses much heavier equipment. The flying of people and of heavy objects is best left to the professionals who have the proper training and equipment.

For our production of Dracula, we needed a bat to fly around the stage. Not just up and down, but left to right as well. You'll see that the bat is able to go up and down via tie line through a pulley. This takes care of the up & down part

Take a close look and you'll see another set of tie line attached to the pulley. This tie line is set up just a clothes line. It's tied to the bat's pulley and pulls the pulley left and right.
This pictures show all three lines traveling through pulleys and coming down to the floor where two people can make the bat fly. One person operates the line to let the bat go up and down and the other takes care of the left & right.