Alternatively, right-click in the Source, Target,
or Spreadsheet pane and click Add Sources and Targets.
The Add Mappable wizard opens.
From the Add Mappable wizard, select messages
from the message sets that are in your Message Brokers Toolkit workspace.
If one does not already exist, a project reference is created
from your message flow project to the message set project that contains the
selected messages.
A Mapping node can
have only one source message, but can have several target messages. Therefore,
you cannot add a source message if one already exists.