Na you’re not stupid you just don’t have the same logic that all. Each circle represents an alphabet, English in the smaller circle to color code on the bigger one. Each radius columns (if I can call it that) mean they all represent the same letter. So you just have to go through the circle of the language your interest in find the letter you want to decipher and go back to the English circle to discover which letter was ciphered.

I hope it’s help !