how to add a link to campaign email?

how to add a link to campaign email?

There are many undocumented  options to simply add a link in an email message?

The links does not work. 

why is not documented https://goo.gl/JJi6T5
in zoho campaign documentation: https://www.zoho.com/campaigns/help/create-campaign.html#Basic_Details

I am sure it is my error for not being a mind reader.

Why make a simple concept for the casual user to difficult>?

anyone else know how to add a link to a zoho campaign email?

ty