The way to transfer between servers (called Kingdoms in the game) is available for new players only — it's called a Server Teleport, and it's available in the game Store and in the main menu (under double arrow).

You can also change the server/kingdom by following these steps: 

1. When you are on your city screen, click on the map symbol in the bottom left corner.
2. Click on the minimap symbol in the top left area of the map.
3. In the same location, there is now the kingdoms button, click it to open the Kingdom list.
4. Select the kingdom you want to join. 

There are certain limitations on server transfers:

• Your game account must not be older than 7 days.
• Your Warlord level must not be above level 15.
• Your Citadel level must not be above 7.
• Some servers can be full and unavailable for teleporting.

All the limits are set by development team to avoid overpopulation and keeping the balance between new and veteran players.