To do this follow the below instructions

Login to website

Go to: Dashboard / Admin > Publishing > Folders

Select the article you wish to link to an article

Edit Article

Once you are in the content editor create text or an image to add a link to an article

Highlight the text or if you are using an image select the image.

Click on the insert Folder/Article link, search for the article you want, select the article and click on Add Article Link.

Done