Many people find these hard to use in the beginning. We use the game solitaire, included in Windows, as a marvelous teaching device. We have found that desktop trackballs are larger and much easier for people to use. Generally, you can purchase a trackball with a serial connector and plug it into an available serial port on the back of the computer and it will work. You have to restart the computer.
Laptops come with many more possibilities.
While many people get used to these over time, you can usually plug in an old fashioned mouse in the back, restart the computer and the mouse will begin working. If the person has better use of their left hand, it can be helpful to reverse the mouse or trackball buttons. Do this in Windows 3.1 by going to Main Group, Control Panel, Mouse. Click in the box and the buttons will be reversed. Many people have difficulty typing capital letters.