Run the 1/4 inch micro tubing drip line up through a drainage hole in the bottom of the window box. Reference this post, DIY Window Boxes, for the window boxes I used.
Once the drip line is up through the drainage hole, fill the window box with soil if it wasn't full already.
Add drip emitters (I used .5 GPH) every 3-4 inches across the window box. I like the drip emitters better than the spray emitters for a few reasons. They keep the water near the soil which reduces evaporation. They also won't spray your windows every time they come on.