Redux 1.2.1 does not show "Sidechain" routing option with PreSonus Studio One

When I try to route audio to Redux 1.2.1 (VST2) within PreSonus Studio One, I don’t see the “Sidechain” option available. Thus, I am not able to route audio to it and record into it.
Would there be an alternate method to successfully sample into Redux from Studio One?