How to use the ball clip
The most important thing here is to keep the ball steady when clipping it on and taking it off. The rocker mechanism that the ball sits on is attached to two metal bands, or tapes, that rotate and tilt the ball to select the letter to be typed. If you move the ball too much while putting it on the typewriter it can cause the bands to fall off their pulleys and become kinked up or broken.
The clip should be snug, not so tight it's hard to get on, but not so loose it can move separately from the ball. I've tested the clips and thrown out the ones that were too loose, but it's possible one might sneak in. If the ball isn't making a complete impression, with tops of the letters missing and smearing on the bottom, the problem is the clip is too thin. Throw it out!
To remove the ball, just follow the above steps in reverse: open the lid, hold the ball steady with one hand, and slide the clip off with the other.