The SuperCell ID - A First Look
Now it will prompt you for the e-mail address you want to use. Note that this MUST be a valid e-mail address and it cannot be one used for another SCID!
...and on the screen that follows, click “Login with SuperCell ID”.
Next you get a list of all the logins saved to this device. Instead of choosing one from the list (where there might be only one in the first place), you want to select, “Login with another ID” and enter the e-mail address associated with your other game account’s SCID. Be sure to click the “Remember Me” box!