As a team Captain you may want to delete a team that you've created under your Profile > My Teams Page.
To delete your team, simply go back to the My Teams Page, select the team you wish to delete and then click the Edit Team button. On the bottom left is the Delete Team button. Please be sure that you wish to delete your team before pressing this button as it will be immediately deleted.
Note: This will not affect any tournaments that you have already joined. You need to contact the tournament organizer for any changes to a tournament roster.