How to create your custom graphics (sprite)?
1. Draw the graphics on paper. Take a piece of checked paper. Draw a rectangle around a 8x8 area. Design the graphics: fill in some cells with the pencil.
2. Calculate the row code for each row in the graphics. Write the following numbers above cells of the first row, in order: 128, 64, 32, 16, 8, 4, 2, 1. Now for each row, look at the filled in cells. In a row, add all the numbers above filled cells together. For example, if your row has the first (128) and last (1) cell filled, write down 129 (which is 128 + 1).
3. Finally enter those numbers in the field above. Some ideas to draw: cup, ball, face, spaceship, horse.
Bonus exercise: try to POKE the codes into C64 or ZX Spectrum.