Firstly, check the Event Manager add-on is installed by going to the Help menu>Feature Manager and check the list of installed extensions and modules. You can install it here if required and your computer is connected to the internet.
Next go to the Setup Menu>Event Manager... This opens a blank Dialog where you can start adding events to monitor and actions to perform. Click on 'New Event' and select 'Level'
Give the event a name. You will then need to select the channel in which the data is coming into and decide on the threshold to be used. You can enter the value into the box or slide the threshold level up and down. Click the up or down arrow according to whether the data is rising or falling (the up arrow should be used in this example). Click OK to complete the step.
You now need to assign the action to the event - in this case adding a comment. Decide if you want the action on the start or end of the event and click on the corresponding text in the dialog. And then choose 'New Action' and 'Add Comment'.
Give the comment a name and enter the text you wish to appear alongside the corresponding comment.
Click OK to complete and then OK again to close the Event Manager dialog. Now the comment will be automated when your recording signal goes above the given threshold.
For full details of the Event Manager options, please see the LabChart help - Help Menu>LabChart Help