How to edit an existing link
When you have a link set up and you want to change it, it is first very important to break the old link before you try to re-link it.
Select the link, and hit the break link icon.
Once you break the link, select the text, click add link icon and type in the URL that you want to link to. Then click the Insert button at the bottom left of the small window. That window will close and your link will be highlighted.
Finally, make sure you save the entire article by clicking the Save button at the top right of the article when you are done.
If you fail to save this last step all your changes will be lost.