Rather than actually seeing the black hole our photograph comes from the light being bent closely around the black holes event horizon. It turns out that having a sufficiently massive object creates a "gravity well" which noticeably bends the very fabric of space time and the trajectory of light within it.
In the image below the ring you see is the gravitational lensing from an entire galaxy, but it produces a similar effect.
In case your interested I recently wrote this article which might give you a more thorough explanation.
Of course feel free to reply to me (either here or under my article) if you have any more questions! I would be very happy to see what I can do. :)
RE: In case you haven't seen it yet.