List Group sections will only use the first link and the link will not be visible as touching any part of the List Group item will initiate the link. All other section styles will show the links as buttons.
To add a link to an article go to the Details page of the article. From there press the Links button. This will take you to the article Links page. The page shows the links your article currently has and a list of articles you can link to. Press the Add button to add a link to your article.
If you want to link to a Page, Section, Event, Walk, Library Collection or an external link press the appropriate button. All the internal link pages are the same format and work the same way. For external links enter the Title and the Url e.g. Ramblers and http://www.ramblers.org.uk/ then press Save. For external links I recommend that you go to the site and then copy and paste the full url including the http: part.
To edit or delete links from your article simply press the Edit or Delete buttons.