Hi wss310,
If you need to add a custom field and a link to it, you can do this simply by going to Settings > Additions > and "Activate Additional Field #1"
You can enter the title (which unfortunately cannot be linked" but when you go to create the text for that under that new field, you can set a link there with the <a> tag. <a href='http://something.com'> Your Text Here</a>
Hope this helps, I will add to our list of updates to possibly allow for just adding that field title and a URL directly from it if that would help.
Regards,
Mike
But if you are asking if you can just click on the text "Learn More", this is not possible, since that custom term is displayed on all custom events if its used, and would therefore link to the same page.