You cant physically add the link....you click on the text overlay in the edit menu, then click edit text, click add link, add the link to the correct page, and close out of that because there is no specific save button to 'save' the link, then usually the main save button up the top of the page to save any changes can be clicked to save your edits but because the system is not recognising any changes made the save button up the top is n to highlighted and therefore you are unable to save anything.
I don't know if this is a system error or something but thought that even so, there might be a custom CSS code that we could use to rectify it nonetheless.