Everything you have played up to this point has been done by simply inhaling or exhaling through the harmonica. However, there are several other techniques used to produce notes on the harmonica. The most important of these is tonguing. This means articulating the sound of each note with the tongue by saying ta as you play.
Here is a single note exercise to help you become more confident with the tonguing technique. Remember to say ta ta ta ta to get the correct sound when tonguing.