Choose a background paper with texture - preferably one with darker outer edges
Grab your Move Tool and squeeze in from the side to whatever width you want your ribbon to be.
If that’s all you want is a straight ribbon, you are done. (Adding style settings such as shadow and glow is optional) We most often use our ribbon in a horizontal position, so feel free to use Rotate or manually turn it 90 degrees using the Move Tool.
If you want a wavy ribbon, your ribbon must run vertical before using Shear -- go to the top of your screen and choose Filter> Distort> Shear. When the Shear screen comes up, grab any point on the ribbon and pull sideways. You can make as many curves as you want - and you can make them any depth you want.
Note: To save your ribbon as a png, make sure it's on a transparent background.
The reason I start with a background paper is because since it is not a plain color, the ribbon will have texture.
The reason I squeeze in the sides to make a ribbon instead of taking a slice from the background paper is that often the background paper has edging and that edging will be on your ribbon if you squeeze instead of slice.
Note the paper I chose has edging.
Excuse quality - these came from screenshots - click on image to see it better