The Cutter Slide is easy to use, but you must practice. Like training wheels on a bicycle, as you get the feel of gliding down the cutting bar without side pressure or tilting, you can put the Cutter Slide back in the box.
This diagram is showing a way to practice without glass. Poster board, or the side of a cereal box, taped to a piece of window glass will let you practice without wasting your valuable glass.
The Cutter Slide is sized for glass cutters that are 5 mm wide. This has become a standard since about 1980. The Toyo pattern head is an example of a cutter head that will work well with your Cutter Slide.
With your cutter head in the Cutter Slide window, pull the cutter down the bar. The device will tip off the bar or bind up if you are tilting your glass cutter. Because the window holds the cutter to the bar, extra side pressure is not needed. Keep an even down pressure as you score from the top edge until off the cardboard (or glass).
Practice on both sides of the bar until you feel good about how smooth and easy it is to score down the bar.