How can I do users login by e-mail instead username?

The SCLogin module has a language file you can use to change the "Username" field text to whatever you want. Additionally, the SCLogin module has an option for "Registration Component". If that is set to Community Builder, the login process will be sent through CB's login flow, which will use whatever setting you have for username that you want.

I hope that helps explain things, but should you need anything else, please let us know.

Thanks,
Alex