Table for Custom Fields
If I understand correctly, you want to add some custom fields to the "Event Participant List" report, as displayed in this screenshot:


If so, you just need to mark those particular custom fields as "Searchable":


Go to Administer menu » Customize Data and Screens » Custom Fields
Click View and Edit Custom Fields in the row labeled Conference_Selections.
Next to each field that should display on the report, click Edit Field.
Tick the checkbox labeled Is this field searchable?.