Scroll all of the views over so that you have a blank area to work in. Good, now lets make the base of our turret. In the top view, create a new block that spans 96 units by 96 units. In the front or side view, resize the block so that it is 8 units high. This is how it should look right now.
Lets apply a new texture to the base.
I chose outboxd . Moving on we get to the body of the turret. In the top view, create a new block that is 16x16 units. Center it right on top of the 'X' marked at the center of the turret base. In the front view, move the body of the turret up so the bottom of it is flush with the base of the turret.