To use a decoration you right click on a portlet or layout and select the alternative Use decoration. A new window will open where you can choose a decoration from a list. Select the desired decoration and click Ok.
You can not make custom settings when the settings are dimmed
The icons below indicate an unpublished and an edited decoration template:
Edited decoration template
unpublished decoration template
If you a decoration is used on a portlet/layout and you select properties on the object there will be a message informing that no settings are available since the object uses a decoration:
Remove decorationRight click on a portlet/layout to remove a decoration, choose the option Use no decoration.