You need to get a Newbie Teleport to switch to another battlefield.

When your commander reaches Level 4, you will be rewarded 2 Newbie Teleports. When your HQ reaches Level 6 or you have registered for more than 6 days, your unused Newbie Teleport will be removed and you will not be able to teleport to another battlefield any longer.

On battlefield map, you can tap World Map icon to view all the battlefields.

After selecting the battlefield, commanders who meet the requirements can move into this battlefield.

Commanders who fail to meet the requirements on HQ level and registration time can start a new game to move to another battlefield through this way. All current game progress will be lost after you start a new game. Therefore, please bind your game account to a Google or Facebook Account to keep your game progress.