A quick way to assign a modulation source to a modulation destination is via drag and drop.
Wherever it is possible to use drag and drop, a modulation drag icon is shown when you hover the mouse pointer over a title header. This is available for the LFOs and the step modulator, for example, but also for the pitch, spectral filter, filter, and amp envelopes.
Procedure
Result
When you release the mouse button, the modulation assignment is created.
After Completing This Task
You can now set the modulation parameters in the modulation row section or in the modulation matrix.