[:C]

you can ban other players using your server's dashboard. In the server dashboard's appearance section there should be something called "server command" in there type in: "/ban (username)" 

Also, if you don't have permission to ban people in game make sure you op yourself using the server's dashboard as well. the command for this is: "/op (username)" 

[hi someone random person is joining my server how do i kick him]

give yourself OP. To do this, go to the console on the website's dashboard. Then, type "/op (name)" and hit enter. From there, you can ban/kick the user in-game.

[Closed server]

you can re-open a server by typing /join (servername) in the minehut lobby.