Is someone acting rowdy and causing a real ruckus? Well, then it's time to call in the sheriff.
Or in the case of Kast, your trusty moderators!
The owner of a party has the ability to manage who gets to be a moderator in the party. To make a person a moderator, click on their name and select "Promote to Moderator", as seen in this image. To indicate a person is a moderator, they get a snazzy silver crown next to their avatar.
If you have lost control of a moderator, you can always remove moderator privileges by doing the same, clicking their name and selecting "Demote from Moderator".
To learn more about what moderators can do, check out this help center article.
Remember to choose wisely who you grant moderation right to, as with great power, comes great responsibility.