The fabric should be cut in half, giving you two long pieces of fabric. Some shops may be able to do this step for you when you purchase the fabric.
Sew the two long pieces together, joining one of the ends. This doubles the length of the pieces.
Before continuing, try the shawl on, and trim the length if necessary.
Iron the fabric as you fold in about half a centimeter around the edges. Pin them as you go. Make sure the folded sides are consistent and that the fabric doesn't fray.
The edges of the fabric can be sewn together by hand, or you can use a machine. A simple slip stitch works well; however, you can use a different pattern if you prefer.
Once sewn together, you can add accessories to the shawl. Many people select a special trim for the edges or use iron-on patches so that the shawl flows with a wedding gown.