How to use the download card included with polyend synth

The palettes are in the Store - you use the code to “pay” for one. The contents of the card is in the Downloads page of website - Synth downloads • Polyend . That includes the stock palettes. (I presume you also got a physical SD card - if not you should contact your retailer. Stupidly, I can’t recall whether it came in the Synth already, or in the USB SD card adapter!)