When playing the recorder, you hold the instrument with your left hand and use your right hand to cover the holes. To make a sound, you blow into the mouthpiece and then press down on the appropriate key with your finger.
The pitch of the note depends on which hole you cover. By covering more holes, you create a higher pitch; by covering fewer holes, you create a lower pitch. There are also some special techniques that can be used to create different sounds on the recorder. For example, by quickly moving your finger off and back on to a hole, you can create a trill effect.
With practice, you will be able to produce a variety of sounds on the recorder and play simple tunes. If you're just starting out, try following along with easy recorder music to get familiar with how the notes correspond to the keys on the instrument.