You can only get rid of people if you are a host/admin in your own server. Someways you can get rid of them are:
1. Kick <node number> in console, I suggest using "ping" command first, find their name, and at the left their number. They are forced to leave but can rejoin
2. Ban <node number>
3. If they do something but end up leaving, use banip in console (I highly recommend turning "Show ip address of joiners" on, marked in options, server options, and all the way down turn it on.)
4. If you are not the host/admin in someone else's server, ask someone who is to kick/ban the person.