How do I centralize my topic or heading on a typewriter?

Using the ruler on the top of the roller or 'platen', make sure your page is perfectly centered on either side of the large triangle at position 40. Then count the number of characters and spaces in your heading, and divide by 2. Deduct that number from 40 to find your starting position. So if your heading is 12 characters long, you need 6 spaces on each side of position 40 and would start at space 34.