Hello Sebastien,
You will either need to click on the
Preview link of your event and go through the registration until you get to the confirmation page (you can't finish the registration in preview mode, though). Or, move your event to Test Mode (click Overview to move to Test Mode or Launch Event). You will be able to finish a registration in test mode.
To make changes to the Confirmation Page, click on
Website & Registration > Registration Pages > scroll down until Registration Summary and choose what you would like to display or hide.
Good Luck!