Rollable Table and missing artwork for token Question

Hi, I have a Doppleganger who I want to be able to take on the form of an NPC in my game. I usually simply drag the character from the journal to a new item in the rollable table to do this. BUT... the NPC I want to use has been provided via a purchased asset and though their token appears on a map in the game and this is assigned to their sheet there is no artwork assigned. The token is not available in the artwork section and I seem unable to get the token on the map into the artwork section. Help appreciated! 

OK I found a way - press z and save image and upload it... a lot more work than expected! Is there a better way?

If whatever you purchased doesn't add the artwork to your art library under marketplace purchases, then what you did is the way to add it to your own asset library.