With the selection tool select the complete bubble overlay (drag from the top left corner down to the bottom right corner) once the image is selected hit CTRL - C
You can also hit Edit menu then click copy and then open the texture and hit CTRL - L
or you can click edit > paste as a new layer
Once you pasted the layer select the layer in the layers menu and click on the Raster layer (Bubble Layer) and on the drop down instead of normal select overlay.
