You can use the modulation matrix to assign CV inputs to oscillators individually. Use the "Oscillator Coarse Frequency" destinations. An amount of 100 will be about 1 volt per octave, provided you have the CV ins well-calibrated.
Unfortunately, Pro 3 lacks Gate In, so you'll have to handle gates via MIDI, or the keyboard, or the Hold button, or send its audio out to a VCA, etc. Lack of Gate In makes Pro 3 a frustrating sequencer target; but its sequencer is better than most eurorack sequencers, and that's where you can really go nuts.
Note that the "Basic Patch" has sequencer tracks 13-16 pre-assigned to CV Outs 1-4, respectively, so you already basically get a eurorack sequencer out-of-the-box.
I have sort of a love/apathy relationship with Pro 3's CV implementation. It's a few basic features (like Gate In) away from being "pretty good."