1- If you have downloaded the game for the first time on your device, it will automatically enter the last server that was unlocked.
2- If you already have a base in the game and want to create a new one,
The game provides you with two options:
- The "new account -( same server)  Feature,  this will allows you to start a new base on the same server as your current one.
PS: this feature will be available only for certain accounts, depending  on their base attributes
-  The Start a new game" Feature, will allow you to start a new base on the game's most recent server.