From here you can:
Host a WiFi game
Join a WiFi game
This game feature requires two devices with the same version of Team Thunder installed
Both devices must be WiFi-connected to the same router and WiFi LAN network.
On device 1 choose “Host Game”
On device 2 choose “Join Game”
Select “Auto” on both devices within a few seconds of one another.
The top red light on each device will turn green.
The bottom lights will turn green once device 2 has also tapped the bottom button to show ‘Ready’.
If not, press “Reset | Disconnect” on both devices and try again from step 1. If this doesn’t work, close the apps and try again (double-tap the main button the front of the device and swipe the app to the side or top of the screen to close an app.) If it still doesn’t resolve the issue, try to reboot both devices and start again.
Instead of selecting “Auto” in step 5, you can also try to connect by pressing “Manual” on both devices. This time, each device will display it’s own IP address. Next to it is another box where an IP address can be typed in. Type in the other device’s IP address. The port numbers needn’t be changed, and they must be identical.
The “Main Menu” button allows you to return to the main menu without losing the connection. Only the host is able to modify the mission number, helicopter and cockpit seat arrangement. Both players can go into their respective Settings Menus, but only the host can decide if the engines will be running or not when the mission starts.
Once connected, mission after mission can be played in coop unless the ‘Exit Button’ followed by ‘Yes’ was used from within the game. That also ends any network connection.