The icon builder is a Sketch file with all the resources needed to generate a FOLIO icon and export it to all the required formats/sizes.
Generate your FOLIO icon in 4 simple steps
Delete the dummy icon, and add your own artwork.
Change the background gradient, by clicking BG style and use the exchange symbols method in the right pane.
Hide the grid clicking the eye symbol in Guides folder.
Click on the preview page to see your icon in context and export it to all the required FOLIO sizes/formats by clicking on the export page.