That isn't how it works. You can wager on either contestant (or a draw), less than the distance or the full distance in a fight. If you want to bet on a ko, bet on less than the distance. There's no reason to have such specific outcomes as "Fighter A by KO in round 8", and it takes enough time as it is to put up five actionable wagers per event.
Go to the Fantasy Boxing Betting forum and open the thread containing the event you wish to wager on. Click in the box next to the outcome of your choice, stake however much you wish (of what you have) and hit submit. You start out with $500.
