The way it works is that there are windows of oppurtunity for you to battle for your team, so you really need to check in as often as you can. Each team gets a chance to challange the king team when their turn comes in a prime time challenge, from 7PM -10 PM eastern. In addition, the first team to make a challenge between prime time can battle the king team, but that is an optional battle for the king team (unless the team with the right to the primetime challenge that night is inactive)
does that help any?