Simply select the action and press play. Your document will be converted into a 16-bit document and a new layer applied to the top of your group/document fixing all the banding in that document.
Unfortunately, this will increase the document’s size dramatically. When exporting assets, copy merge and export to a new, 8-bit document. This will reduce the size while keeping the beautiful gradients.
Note: You must apply this action inside every smart object.Read more about this technique