The trick is to use a monospaced (non-proportional or fixed-width) font on your computer. This is what the typeface in most arrangers use. In regular fonts, each letter takes up a different amount of width, which, if then displayed in a fixed width font, makes a huge difference to where along the line a letter is displayed.

Probably the one you'll almost be certain to have in your computer is Courier, a typewriter font...