This NASA article explains how you can't really "see" black holes but you can sort of see the force they exert on surrounding objects. It has some cool artist renderings of black holes too:
Because no light can get out, people can't see black holes. They are invisible. Space telescopes with special tools can help find black holes. The special tools can see how stars that are very close to black holes act differently than other stars.
And here's another article from University of Arizona about Quasar J0100+2802 that includes a cool depiction of what's going on with black holes too.
