Recall pedal C is the first C under the bass clef. A pedal note is any note under pedal C. Use pedal notes when you want power.
Pedal notes must be voiced carefully so as not to muddy the chord. Underneath, pedal Bb is reinforced by its octave. The region between pedal and bass Bb is clear of notes.
Here are various voicings for you to listen to of the C9 chord written for 4 trumpets and 4 trombones. The third and fourth chords make use of pedal C. In each chord there is a different melody note. For the last chord the melody is so low the trumpets are not harmonised. They all play the same note (in unison).