can you add specific fields (if they are numeric) into another field?

If you would like to look at the form it is MGGKC State Conference Registration

https://www.jotform.com//?formID=61037016688154

Can Total Amount for Ticket Type(s) chosen

and Total Amount for Friday A La Carte

and Total Amount for Saturday A La Carte

and Total Amount for Your Apparel

be added together and fill a field (Total Amount for the Conference) without the user filling it?

(I would like to use that field to then calculate (conditional using a value from Enter Qualified Volunteer Password) the Total Amount You Owe field.)

Is this doable?

Yes, that's possible using form calculation widget. Here's how to perform calculation in your form.

If you need further assistance, let us know.