READ THE README FILES!!!!!
These are highly engineered objects. They will only work as intended if they are printed using the recommended orientation, layer thickness, and infill settings.
You may have to reorient the glider on the print bed if your software does not allow you to change the printing orientation....the first layer must be front-back, the next one left-right....both in line with the fuselage and wings.
A 45 degree standard printing orientation will cause the wings to flex asymmetrically, seriously affecting performance (the glider will turn violently at any significant launch speed). The jets may perform ok even if printed a little wrong, due to their more rigid wings.
Watch the videos.
You will need some room. A park or something similar is perfect. Respect bystanders, and wear eye protection....these little guys have a way of coming back to you, and fast.
They really do fly. Keep at it, you can get the same results with a properly printed and adjusted glider.
Unless you are experienced tossing gliders, it will be much easier to start out with a rubber band and launcher (print one from my launcher and tools thing). Use a long, thin rubber band, not a wide one. Start out small, holding the tail, pulling back a little and releasing until you get the hang of it.
Adjust the glider in small increments until it flies straight before going for the big time.