To set Unsubscribe URL using WYSIWYG Editor, first select your WYSIWYG Editor from Campaign > Content.
Once the editor opens, select any text and the highlight it. Once highlighted, click on Insert/Edit link and enter the merge tag “{{unsubscribe_url}}” in the URL field of the Insert/Edit Link popup box.
Select Unsubscribe URL from Link list and then click Save.
Click Done editing and exit from the editor. Now your Unsubscribe URL is ready.