How do I add lexis nexis authentication to a created template?

The Knowledge Based recipient authentication is chosen on a per Recipient basis if enabled for your DocuSign Account. To check whether your Account has this option, create a New envelope, add a Recipient, select "More" to the right of the Recipient then "Add Access Authentication" then from the dropdown see if you have "Knowledge Based $". Remember this is a per usage charge.

Here is a DocuSiogn article on Recipient authentication...

https://support.docusign.com/en/guides/ndse-user-guide-recipient-authentication