If you have saved your mask image to a file, then open it and minimise it - be sure you know what it is called!!
Open tube, duplicate (shift d) close original and resize 75%, uncheck all layers
Duplicate layer
Click on glasses to hide top layer
Activate Bottom layer
Muira meister copies - increase the number so that the tube covers the whole layer
Gaussian blur 7
Dsb flux blast - do this four times using the different settings: up, down, left and right percentage 20%
Duplicate layer
Load mask from image - use your drop down menu to select the mask. Choose source luminence.
You will not be able to see your mask - but don't worry, it is there
Delete mask layer - answer yes to popup
Merge group
After this next step your mask will become visible
Inner bevel:
Drop shadow 4, 4, 95, 7
Activate tube layer
Give tube a drop shadow again, settings as before
Add any text you wish
Merge
Add border size 1 black
Add your watermark