Write out the rhythm section parts the bottom staff of your manuscript paper. The rhythm section is comprised of drums, piano and bass in this musical ensemble. Write out the rhythm or groove you'd like your drummer to play on the bottom staff of the manuscript paper. Write out the bass line for the bassist, as well as chord symbols for each chord, on the staff above the bottom staff. Do the same for the pianist, writing out a melody line and chords on the staff above the bassist's part.
Write out your lower horn parts -- baritone sax and third trumpets -- on the section above that, giving them a main melody line on top of the rhythm section parts you composed in the previous step.
Write out your alto and soprano saxophone and first and second trumpet parts on the two top staffs that are left on the manuscript paper. These melody lines should be the main melodic line that the listener will hear.
Write out any sections for solos on a second sheet of manuscript paper, dedicating each staff to a particular instrument. Write out the number of measures for the soloist to play.