If you want to personalize your account a bit, go to the edit profile page (click the dropdown button next to your username).
Most of it is pretty self-explanatory, however, below the video are a few useful tips:
If you created your account with Facebook/Twitter/etc, and want to have a way to log in with username/password, you can create a new password ('Change password' and 'Verify password' fields).
You can connect/disconnect Social media accounts for one-click login. Simply click on of the "Connect" buttons on the Edit profile page.
To be able to use the password reminder and new turn reminder (in Casual games), please fill in your e-mail!