Step 4: The math stuff
First you're going to want to measure the length and the width of your material and cut any edges so that they're straight, incase whoever cut them at the fabric store didn't cut a straight line. A cutting board will help with that.
Now, decide how far you want the dots from each side. Don't forget to use both sides, and leave about .5-1 inch all the way around the blanked for seam allowance if you're going to be putting a back on it. Then decide how big you want your circles to be and multiply it by four (since going across there will be four circles, one of each color). Subtract both of those numbers from the total width. That will be how much you can use overall between the circles. But now you have to divide it by three, which will be how much space is between each of the circles.
So, since my piece of material is 60 inches wide and my circles are 6.5 inches in diameter and I want them about 8 inches from each side I will be able to have 6 inches in between them.
For figuring out how far apart your same colored circles will be, just do the same thing as you did before, but the length may be more and you'll probably want them further from the bottom and the top. Instead of multiplying the diameters of the circles by four, you'll multiply it by six, and instead of dividing by three, you will divide it by five. Got that? Good.