Form field in alert email

We just launched a new website, including new Demo Request forms. The Demo Request form is a Marketo form, and it includes a Comments field which we did not have on our old form.

I am trying to update our email alerts to the sales team to include the new Comments field. However, Comments isn't a default token, and I can't figure out how to add it as a token.

Any tips? I am new to Marketo, and still getting comfortable with the system.