On the voice track.
On the track the knob is instant, and one Velvox covers every clip on it.
Resolve: the Fairlight page, Mixer. On your voice track's strip, click + in the Effects slot and pick Velvox.
Premiere: Window > Audio Track Mixer. Show the effects (the small triangle at its top left), then pick Velvox in an empty effect slot on the voice track.
Final Cut: it has no tracks, so put Velvox on the voice clip, or on a compound clip holding the whole voice.
Not on the clip in Resolve. A clip effect is rendered ahead of time, so every knob move is heard a second or two late.