When you add a server, it just puts you back on the main screen and it doesn't show up.
Comments 3
Sammy is correct, there are no servers on 0.12.0, at least for Windows 10. This is probably because Windows 10 is on 0.12.0, but MCPE is on 0.12.1, which implements a couple more things than the Win10 release did.
There is no servers at 0.12.0