Authentication should be ensured over either SSH or HTTPS. Since it is a little more tricky, i will share SSH steps.
We need a key pair: (Private & Public) We can generate them via windows command line or PuttyKey Gen:
Put the files under:
Put the PUBLIC (not private) context to remote:
Add key to local settings as well over GitBash:
Finally, if we want to use SourceTree, we should add the key to it also: