Most PC Access commands are on large buttons. For example, when you start PC Access, after a brief introductory screen, you see the PC Access Main Menu window. (Each window has a title at the center of its top border.) The Main Menu window has an array of buttons. Each button has a 1--2 word command name, and a small picture (or icon) suggesting the command. You tell PC Access to run a command by clicking its button with the mouse. For example, to call the MLS, you click the Call MLS button.
You can also select buttons with the keyboard: press the Tab key to highlight the next button, or the Shift-Tab key to highlight the previous button. If you press the Enter key, you select the currently highlighted button.