It is very easy to patch modulations: just open the module you want to modulate, select a modulation source and adjust the modulation amount (you can patch multiple sources into the same modulation input, each source with its own amount, without the need for a summing module).
For instance to modulate a filter frequency with an LFO, open the Filter module, cursor to the Frequency Modulation input, push the big data knob, select LFO1 from the list of modulation sources, cursor one click to the modulation amount right next to it, adjust it. Et voila!
However, it's a little more involved if you want to insert a CV modulator in between, in order to modulate the modulation amount. In the example above, you would add a CV Modulator module, patch the LFO to the input of the CV modulator, patch the output of the CV Modulator to the Frequency Modulation input of the Filter, and then select the modulation source for the CV modulator.
It's not complicated when you already know how to use a modular synth. You only have to get used to the nagivation on the display.