Here you are defining the "segments" of your light-display. Use this to split the strip in stairs, blocks or any other configuration. Normally you would define a segment, for each cut you have made in the strip. But you could do other things to get fancy results. Each segment will be represented in the "matrix", by the number just below the number. Each segment should have it's own box below.
Here you are defining your matrix. A matrix is really nothing more than a 2-dimentional array, or a list of lists. This is not a mathematical array, meaning each "row" can have different lengths. Use this to stitch your segments together. Each "box" should contain the number of the segment it is representing. By pressing the double-arrows on the box, you can "invert" a segment. This means counting from the other end. Use this if you have the segments in a snake-layout.