If you've played Call of Duty: Mobile before, you'll automatically log in with the account you used last. If you'd like to log in with a different account, you'll need to log out first.
- Tap the Gear icon at the top of the main screen.
- Tap the Other tab in the far right end of the top row. You may need to swipe the tabs row to see Other.
- Tap the Logout button in the bottom right-hand corner.
Logging out will take you to the log in screen where you can log in using a different account.