Carefully cut out your square along the pencil line. Throw the small scraps in the garbage.
Find a row of squares. Decide where you will add your square. Make sure it is facing the right direction.
Pin your square down. 2 pins should be enough.
Use a 5/8 Seam Allowance and sew along the right side of your square. Start and end with a back stitch.
Trim your threads. When you unfold your square, you should have a finished seam attaching your square to the one next to it. Return the row of quilt squares to the "Logo Quilt Bin."