I ran across your post when hunting for an answer to the same question. Signed up here just so I could share this because I found the way through trial and error and, probably folks with experience will chuckle that we didn’t figure it out faster. Oh well, one day we will be folks with experience also. ?? Here’s what I did:
<a href="<?php the_field ('url-field-name'); ?>"> MUST HAVE TEXT HERE</a>
Put that ‘must have’ in caps because it is the essential part. Just like when we add a link via the wysiwyg editor, we have to have something/word for the link to ‘attach’ to so that there is something to click on.
I hope this helps if you have not already figured it out, or at least helps the next person. ??