There are many different ways to get your modular and your computer to talk to one another, MIDI to CV, CV to MIDI, trigger to MIDI, excellent solutions from Expert Sleepers and more. However this new Max4Live device built by two piece electronic outfit Skinnerbox now makes it super easy (and free) to use your modular to control Live.
Usually for a computer to understand control voltage from your modular you would need a DC-coupled audio interface, but the CV4Live device can fully understand your control voltages.
It can be used for taking CV and triggers/clocks from your modular, allowing you to modulate parameters within Ableton from your modular. You can even trigger clips or clock Ableton from your modular using the Clock4Live device.
Check out Skinnerbox for more info.
The first standalone semi-modular from Pittsburgh Modular