Search through all of our Frequently Asked Questions over here.
You can only score a round after a round has ended.
When a round ends, you'll receive a push notification prompting you to score. Make sure your round scoring push notifications are enabled for this.
If your notifications are disabled, go to the Scorecard page of the relevant fight and click "Tap to Submit for Round X".
You'll then receive options on how you want to score the round. Enter your score and click "Submit".