Demeter, this is quite difficult without the ability to draw for you, but if this doesn't make sense tell me and I'll try again:
Starting from the top left, the first block is made up of the first four blocks of the top row, the first five from the second row, and the first four from the third row.
If you repeat this shape for rows four, five and six, and then mirror to the right hand side. In the middle then you will see the two different shapes.
If you then mirror the whole lot to the bottom half, you will have 8 identical shapes, and 4 different shapes, all containing 13 lights.
Hope this helps