To store the coordinates of the current cursor position (the values of the data points in x and y) press the space key. This will record the point in an internally kept table. Its content is displayed in the Data Table window. This docking window can be made visible by selecting the View->Data Table menu item.
If you make a mistake and want to delete the last scanned point select the Edit->Delete Last menu item. Edit->Delete All will erase all data points stored.