Based on page 36 of the manual... You don't.
Other than the special pre-count pattern -- which is in 4/4 -- the R24 metronome is just even ticks.
Page 58 indicates that you can change the time signature for inputs to the Track Sequencer (which implies that each assigned pad would then be based upon that signature); Page 68 indicates you can specify a time signature when creating a rhythm pattern.
In contrast, the R16 manual page 34 shows that ITS metronome does allow for specifying #/4 time signature.
IISS Elusive Unicorn (detached)
Superscope PSD-300; BOSS BR-600, Zoom HD16cd, Zoom R16, BOSS BR-800, Zoom H2n
Now to learn to play an instrument