The D finger strikes the E and C keys. The K finger strikes the I and , keys. When you type the comma, always put a space after it – not before.
Place your fingers on the home-row keys. With the D finger touch the E key, back to the D. Then touch the C and return to the D. Repeat this three times while you say the letters aloud.
Now, with the K finger touch the I key, back to the K. Then touch the , and return to the K. Repeat this three times while you say the letters aloud.