To read a codon, start at the middle of the circle and move outward.
Step 1. To decode the codon CAC, find the first letter in the set of bases at the center of the circle.
Step 2. Find the second letter of the codon A, in the “C” quarter of the next ring.
Step 3. Find the third letter, C, in the next ring, in the “C-A” grouping.
Step 4. Read the name of the amino acid in that sector—in this case histidine.