You can save your game account by linking it either to Game Center or MY.GAMES ID.

Game Center

 You are supposed to be logged into Game Center with your Apple ID:

1. Go to Settings;
2. Find Game Center and make sure it's enabled (toggle on);
3. Continue with your Apple ID;
4. Go back to the home screen and launch the War Robots app;
5. Proceed to the in-game settings menu, scroll down to the "Authentication" section;
6. Tap the second "Save Progress" button to confirm logging in to Game Center via the game.

The above will work only in case you don't have another War Robots account already linked to this Game Center account. If you'd like to save a WR account, but you're logged in with a Game Center account that already has another WR account linked to it, you should use another Apple ID.

Server authorization (MY.GAMES ID)

1. Launch the War Robots app;
2. Proceed to the in-game settings menu, scroll down to the "Authentication" section;
3. Tap the first "Save Progress" button to log in to your My.Games account via the game.