Teaching parakeets who were never let out of their cage how to fly?

It's all in the title! I was given a pair of parakeets who are about 2 years old I believe. They have never been let out of their cage which saddens me and they are very skiddish around people. I let one of them out in a small room and he just kept hitting the walls and panicking whenever I came near. Any tips? I've had a bird like this before and I was wondering if there was any other way to train them to fly around without them crashing and falling. It scares me that they could get seriously injured.