You enter the bearing and range into the TDC. Once you have entered two bearing/range entries, switch to the speed dial, and click the stopwatch.
The crew will do the calculations on their plot (which they keep hidden from you so you can never ever look at it
), and will tell you the speed and course. Enter the speed, and go to the AoB dial. You can approximate the AoB visually. Once you enter the AoB you guessed, look at the target dial on the left hand side of the screen. The target's AoB will be reflected there, and the outer ring shows the course.
Remember, the crew told you the course when they told you the speed. Fiddle with the AoB until the correct course is shown on the dial.
Keep in mind that the game will calculate the speed and course based on the two range/bearing fixes. If you mess those up, you mess up the speed and course. There's other ways to do it, one of my favorites involves a slide rule. This method is just the way the game is set up to help you simulate actually having a tracking party.