Managing your attendees fees can be done on the Ticket or Registration Type Tab of your Event Configuration Dashboard. Fees are set at the ticket level under the Ticket Price section and are calculated for the attendee and everything they pay for as part of their registration.
Note that the first two options are specifically only for Brushfire fees. Any other fee you would like to cover, ie. payment gateway fees, can be managed by utilizing the Custom Fee option.
The system will default to passing along the Brushfire fees unless otherwise edited. Also, you can only pass along fees when the currency is set to USD.