Use a suitable pen (e.g. a black permanent marker of fine or medium thickness) to draw the characters the way that you normally write. Make sure you draw your characters into the designated cells.
Only characters that are written down on the template are added to the font, so if you only need a few characters, then only write those down. If you don't want accented characters, you can skip page two of the template.
All cells (except the signature cell) contain horizontal guidelines (actually four little marks on both left and right side of each cell) that should help you write the characters in the right dimensions, and in the best possible position in each cell.
When you've drawn all characters you want to include in your font go to:
and scan the completed template.