You're very close. Scroll down to the Tournament History section. Right-click on the add-on you want to remove and select "Undo Add-on". For the other player you can insert the add-on in the same way. In the Tournament History section, right-click on another event (the bust-out, for example) and you can insert an add-on between the event you clicked and the previous event. It will automatically be given a time halfway between the two events.