To store the coordinates of the current cursor position (the values of the data points in x and y) press the space key. You will hear a gentle bottom click sound as audible confirmation. This will record the point in an internally kept table. Its content can be viewed in the Data Table window that can be launched via the View->Data Table menu item.
If you made a mistake and want to delete the last scanned data point select the Edit->Delete Last menu item. Edit->Delete All will erase all data points stored.