Hi @Ken1963,
There's a couple of options for you:
1) You can right-click on your layer and select "rasterize this layer". This will allow you to use the Content Aware Fill, but depeding on your images, canvas size, etc., you can lose quality. If you use this option, be aware that you won't be able to enlarge it later without losing quality. Also, if you decide to work on the original image (for instance in LR), it will not update the file used in PS.
2) You can double-click on the layer, it will open it in a new tab and you will be able to use Content Aware Fill. You will be working on the original sized file, so no loss in quality here. When you are done, you can save the file, and go back to the file where you imported it, the modifications should show. My advice would be to choose this option and to do your editing on a separate layer so you can go back easily to the original if needed.
I hope this helps!