Click the Add Annotations 
button on the Plot toolbar.
Overview
stPro provides a mechanism whereby a user can add a note or 'Annotation' to a trend. This can be useful when wishing to label periods of particular interest or for remembering when specific plant events occurred. The facility can also be used by shift Operators to pass information on to other users.
Annotations can either be either public or private and can be associated with an item or just a specific time period.
Note: Annotations are supported for all Graph types, but cannot be used when connecting directly to an OPCServer as they are stored with the SDRs on the Collector node.
To add an annotation to a Graph:
Right-Click on the desired plot, click Annotate Graph and enter the desired Annotation.
or
Click the Add Annotations button on the Plot toolbar.
Tip: If the plot cursor is active, then the time for the Annotation will default to the current position of the cursor. If it is not, then the time will default to that of the latest scan.
For more information see the section on the Annotation Bar.