Add Text Tags to Excel

I am trying to prepare an excel template to automatically come into AdobeSign with signature fields instead of manually placing them each time.

According to this reference, this can be done in excel.

https://helpx.adobe.com/ca/sign/using/text-tag.html

I've tried just placing the text and converting to PDF, but they just come through as plain text.

How do I add a text tag to a document in excel so they show as fields in AdobeSign?