I'm using gitlab.com, and I'm not that used to with SSH Keys. BTW I've managed to create a SSH Key in my Windows 8 PC using cmd and Git bash. And I've managed to add that to my gitlab user account.
Now in my project "Deploy Keys" I'm seeing:

If I try to paste the same key here too, it's not adding because it's already taken.
The question can be answered by either of the following two:
- How can I add the existing one then? or,
- How can I make my SSH key active for my project, so that I can push into private repo of gitlab without username and password prompt?