Nitelighter not fitting AG Emerald Isle pool?

[matt4x4]

You are supposed to remove the top rail, hang it over the wall and reattach the top rail. If your top rail "pinches" the wall with a U shape, you will have to change your mounting method and adapt as necessary.
If your top rail is double walled - ie - cross section like this (roughly):

/~~~~~~\
|___||___|

and the two verticals in the middle are too close together to cap the light top, the I recommend you just screw the light upwards into the top rail from underneath just inside the pool wall.

Edit - I just looked at your pool - it's resin, so yes, it'll pinch the top of the wall, and the width of the nightlighter is too wide - so, one of three choices -
1. do as I stated above and screw in from underneath.
2. Return it and buy an aqualuminator light - my choice - better light anyways - and get the LED model while you're at it.
3. Dremmel the area out of the resin top rail where the light should go.