First you need some tank sprites and you can make your own or here are some free sprites:
Once you have your tank sprites set up you need to add the 8 direction movement to the tanks.
The arrow keys will work to drive the tank without any events needed.
Then you need a bullet for them to fire. You can use that bullet sprite or make your own.
Give the bullet the Bullet behavior.
The bullet only fires at the angle it is set to so you have to set the angle to the angle the tank is facing.
On Key Pressed: Create bullet at position Tank X and Y. Set Bullet Angle to Tank Facing Angle, Enable bullet.
That is pretty much all you need to make a tank move and fire.
Once you get one tank working you can start creating an enemy tank and that will use the In Line Of Sight and Follow Path Behaviors so study the tutorials on those Behaviors.