There are a few different ways that you can transfer letters to dark fabric for embroidery. One way is to use an iron-on transfer pen. These pens have special ink that will show up when you heat it with an iron. Another way is to use carbon paper. This is a type of paper that has carbon on one side and tissue paper on the other. When you place the carbon paper under your fabric and trace over it with a pencil, the carbon will transfer onto the fabric and create a template for you to follow.