I have a 4 channel receiver and recently bought a plane which requires
2 servo's for the ailerons...

I bought a Y spliter to run from the receiver controling the servos...my question is this:

One servo will need to move in one direction and the other in the opposite to operate the servo's correctly for the ailerons. I'm a bit confused thinking that when I wire and mount them that they will both
move up at the same time or down at the same time. How would achieve
having them move in opposite directions?

Mount one servo with with the servo post closer to the front of the wing and the other with the post closer to the back of the wing, or mount the both facing the same way and put the pushrods on opposite sides of the servo.

Flyboy's right, but let me put it this way : it is not correct that 'One servo will need to move in one direction and the other in the opposite to operate the servo's correctly for the ailerons.' With the Y connector, both servos will move with the same rotation. You have to put the arms on so that the ailerons move correctly.

Good luck!
Dave Olson