First, make sure that you have modulation assigned to something (Ex. Pitch, Filter, etc..).
Patch from the KB GATE output in the ARP/SEQ module, to the SYNC input in the MODULATION module. Now, each time a note is played, the cycle of the modulation LFO will be reset with each new note. Slower LFO speeds can act similarly to a second envelope, while faster LFO speeds can impart swing, act as a flam / ratchet, or even be used to mimic delay effects.