In the bottom of the COSMIC window (on the Sparc screen) there are two panels for controlling the guider: position angle and focus.
In order to find a guide star, move the mouse to point at the GUIDER POSITION ANGLE button labelled ``+ sp -''. Pressing the middle mouse button will then toggle between FAST and SLOW speed settings; pressing the left/right mouse buttons will cause the guider position angle to increment/decrement. Increment the position angle steadily until you start to see a star moving across the TV screen (right to left).
Once you find a star, try to focus the guider. Move the mouse to point at the GUIDER FOCUS button labelled ``+ -'', and press the left and/or right mouse button to focus the guider. You will notice the guide star move up or down on the screen as you change the focus. When you are happy with the focus, either start guiding on the star (next section) or continue moving the GUIDER POSITION ANGLE until you find a sufficiently bright star to make you happy.