The above tutorial link is not available. Is there another link?
Is it an ordinary file like jpeg or PNG? If so you could open it in the Expert workspace and create a brush. From the menu choose:
Edit >> Define Brush
Give it a name E.G. My Watermark and save.
Then select the brush tool and from the pull-down list find your new brush, usually at the bottom of the list.
You can then apply the watermark to images with a single click.
The beauty of creating a watermark brush is that you can adjust the size and opacity before applying it to individual images.
jpeg I opened a picture clicked on Edit and define brush is grayed out
It will work with jpeg but the image needs to be quite small for a brush. Try cropping.
I usually start with a new document:
File >> New >> Blank File >> OK
Its then possible to set dimensions and resolution for a logo and to choose transparent background. Using:
File >> Save for Web means you can choose PNG24 which maintains the transparency.