If it's like a tank, you only use your motors to turn.
If you have an additional motor to get lift I don't know how to achieve that.

But for turning just with the 2 motors you can use Wing-Tail Mix type: EVELON

See your manual for which 2 channels on your receiver you need to connect your to ESC's. Then you turn on the EVELON Wing-Tail mix. You should set up the Aileron and Evelon on your right stick to go both 100%.
Then you might need to set it up on mixing so that they go down to 50-80% when you turn.
This would give you both motors 100% straight forward and 1 motor decrease thrust to ex 80% when you try to turn and the other motor still at 100%.
in the Brushless thread I have explained how I set up a tank in this matter, so if you find that thread I explain it on a Futaba 10C and I have "explained" all my settings.

Isn't there a rudder on this machine you can put a servo on? It looks like it.