1. Place the first three fingers of your left hand on the keys closest to you, starting with the index finger.
2. Place your right thumb on the key just below the one your left index finger is on.
3. Place your right first finger on the key above the one your left middle finger is on.
4. Place your right second finger on the key just below the one your right first finger is on.
The resulting combination of open and closed keys should produce the note B natural.