Silent Night by Franz Gruber is another example of a well-known tune that uses the primary chords. Click on this link, and fill the empty bars with one of these chords but this time try to create a more varied bass line in contrast to the tune. By doing so, you will develop rhythmical interest. An example of what you could do is given in bars 1-8.
It means that you repeat the material from the preceding bar. Therefore, the tonic chord (E♭) remains throughout bars 1-4. The dominant chord is repeated in bar 6, etc.