When you edit a field in RSVP Pro there is a series of questions near the bottom "show in form only", "show in detail", "show in list" etc. It is this "show in list" that you want to be yes (and "show in form only" to be no).
Then in the RSVP Pro config you should set the config option to display custom fields in attendee list views.
Please note that this will show all your custom fields on all your events so if you don't want some to appear you need to set the "show in list" to be no for other fields.