Get the camera actor and ‘get’ it, then you want to be setting it’s transforms on the button press, so right click and find ‘set transform’, plug your camera into that, you might want to find the current transform of the mesh it is following, so you can further ‘get actor transform’ then add your own offset to it with a vector.
That should give you enough of a push in the right direction for you to play around with nodes and variables 
Check out the really helpful epic blueprint tutorials too.
https://www.unrealengine.com/blog/blueprint-basics
If you are still struggling after that, dissect the content example stuff to see how they have done it.