Remember that the aim is always to work new knowledge into your singing until you can use it naturally. This is usually achieved in several steps.
When working on dynamics, another useful exercise is to apply dynamics to a major scale, i.e., sing do softly and gradually increase the volume as you ascend through the scale, until you are singing loudly by the time you reach the do an octave above. Then do the same thing as you descend the scale. Next try starting loudly and get softer with each syllable until you reach the end of the scale.
The final step in adding dynamics to your singing is to apply them to a song. This is a much more personal thing and also depends on the emotional content of the lyrics. Obviously some lyrics call for a quiet, subtle approach while others need strength and volume.
Listen to recordings of your favorite singers and pay particular attention to the way they use dynamics. If you are singing with an accompanist or a band, you will need to rehearse your dynamics with them so that the music can "rise and fall as one". When this happens, it feels great as well as giving the ensemble the ability to move an audience more intensely.