General Description: 
  For a dotted quarter, first enter a quarter note. For a dotted half, first
  enter a half note. Then lengthen the note by one-half of its value to make
  it a dotted note. For instance, for a dotted quarter note, enter a quarter
  note (one beat in 4/4 time, then increase its duration to one-and-a-half 
  beats. 

Here's the step-by-step for entering a dotted quarter note: 

1) Using the Pencil tool and with the Quarter Note selected in the Durations
   Palette, enter a quarter note. 
2) Switch to the Pointer tool. Double-click on the quarter note you just
   entered (in step 1, above). 
3) A popup menu should appear. Select Duration... from the popup menu and
   click on Set. 
4) In the Duration dialog box that opens, change the Steps from 0 (zero) 
   to 50. This will add half of a beat to the duration of your quarter note. 
   Then click OK. 

The quarter note you entered will now be a dotted quarter note. 

By changing the note values and durations as appropriate, you should be able
to achieve the same results for entering a dotted eighth note, dotted half
note, and so on. 
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