Thanks Kevin, tmuser/tmuser connects in Go->Connect to Server. After this successful connection, Time Machine asks for password for the first time and it connects as well.
I'm very new to Mac. Maybe these steps are obvious for others

. I didn't see tmuser/tmuser anywhere. Can you please add tmuser and Go->Connect to Server steps into the article as a note for others like me
Some more info to be sure about I'm doing everything right. (Attached screenshot)
* In time machine, I can not connect auto found MyTimeCapsule on "MyTimeCapsule".
* In time machine, I can connect MyTimeCapsule on "192.168.1.100". I mounted this in Go->Connect to Server step.
* In Go->Connect to Server, When I try to connect with name instead of local IP, server can not be found.
My questions:
* Are those symptoms expected behaviour?
* Do I have to mount MyTimeCapsule prior to use in Time machine? Otherwise I cannot connect as described.
* How can I change root and tmuser passwords?