Guitar plugins require a precise input level to emulate the behavior of a real amplifier's front end. Connect your guitar to a Hi-Z (Instrument) input on your audio interface. Adjust the interface physical gain knob so your hardest strums peak around -12 dB to -18 dBFS within your DAW meter. If your signal is too hot, the virtual amps will clip harshly; if it is too quiet, you will lose dynamic response and sustain.
Once the download completes, follow these instructions to install the plugin on your system: Helix Native Mac Download