For the simplicity, XY graph is used as an example to show how to add the cursor.
To add a cursor to the graph, follow the below steps:
Right click on your graph.
Go to "Properties".
Select "Cursors" from the tab and click "add".
You can change the colour of the cursors and the line thickness in the pop up window, you can also allow free dragging to arrange the position of the cursors.