Newbie Question

I have started playing around with Roll20. I've figured out how to upload maps and drag tokens onto the map. I'm a GM so really only interested in monsters and npcs. I don't want a character sheet for all my monsters. So I've read you can just drag and drop creatures from the compendium onto the map and boom, everything you need is there. Well for instance, I dragged a black dragon (in the D&D SRD) from the compendium entry onto the map and all I have is a square with a placeholder picture an in the settings, just a name.  What am I doing wrong?

The SRD doesn't contain any licenced art so all you get is the statblock as a journal and a default token. You'll need to add your own art and link it to the token to get the most out of it. Purchasing the monster manual or other source books that contain monsters will unlock the full package from the compendium drag and drop but obviously there are costs involved in that approach :)

And even when purchasing an item, they can only include the art in the book. So a few creatures that do not have an illustration in the book do not have art in their token.