Applied Parameters:
EditorKind=CustomPaint_PlaceComment
Summary
This command is used to place a comment in a PCB, PCB library, schematic, or schematic library document that is saved in a Workspace.
Access
Click 
near the top-right corner of the design space.
Use
After launching the command, the cursor changes to a crosshair with a blue circle at the center. Position the crosshair where you want the comment located on a PCB, PCB library, schematic, or schematic library document then click. The Comments panel opens in which you can enter then post your comment.