This is how to use it:

http://www.sweethome3d.com/userGuide.jsp

It's right in the end of the page.

As the description says in the link in my previous post, it copies the colour or texture you have set to an item to other items you have selected. For example it can copy the texture of the sink to the bathtub and the toilet.

Let me know if it doesn't cover your questions [:)]