if you click 'STRG + V' or 'Edit-> paste' to paste a layer, a floating layer will appear
you can transform that layer but not paint on it
you must anchor that layer by clicking on the little anchor icon and then it will merge down, or click the little layer icon instead, to get a new layer and then you will be able to paint on it
also you can use Edit -> Paste as new layer
or File -> Open as layers (if you have a picture on your hd somewhere, that you want to open as a new layer)
Attachment:
Layer.png [ 27.56 KiB | Viewed 1170 times ]