Switch to the Enterprise Service Tools perspective.
In the Outline view, right-click the Elements and attributes folder, then click Add Global Attribute on the pop-up menu. A global attribute of type string is immediately added and is assigned a default name.
Either type a new name for the global attribute or press Enter to accept the default.
You can now configure the local element to your exact requirements. For further information on configuring message model objects see Configuring message model objects.