1. Make active the layer that contains the object that you want to edit.
2. Select the object you want to modify.
3. Click on the Edit Object tool.
4. You will notice that the points of the object appear numbered in the order they were created. If you want to select a point, you need to click on it. You will see that the point changes its color (from green to red).
5. To move a point, first you need to select it and then, while holding left-click, locate the destination where and drag it. Finally, release the button.
6. To add a new point, first point he mouse where you want to create it and then left-click there. The new point will be created.
7. To delete a point, first you need to select it (its color will change from green to red) and then double-click on it. The point will be deleted.