Assuming you’ve installed the software properly, and your DAW has already found it - for most DAWs, it works the same as any other instrument VST. However, as there are four dependent VSTs, you must be sure to start by opening Orb Chords first, and then opening the others (Melody, Arpeggios, Bass). Orb Chords acts as the Master VST and is required to be loaded before the other plugins will function.