If your account is not link on your Facebook account, please check this out on how to link it using the settings menu: How to link your account using the settings menu.
If your account is already linked in Facebook account, here's how to log in using your Facebook account.
REMINDER: Make sure that your War Pirates account is already linked to your Facebook account before following the steps below:
1. Tap the "Facebook" button on the left side of the screen, then Facebook user login will pop up.
2. After that, enter your Facebook account and tap Login button.
Your War Pirates account will show up right after you login.