Hi. Each command is listed with syntax in the "command" table of the "world" database. Try to execute "SELECT * FROM command;" without quotes on world database. You can also see commands in source code at https://github.com/TrinityCore/TrinityCore/blob/6.x/src/server/scripts/Commands/
Check if you got ports open on the servers router (3724 and 8085 default).
I assume you already have set the correct ip adress in realmlist table - auth database and same ip in realmlist.wtf. If you got a DNS you should use that instead of the IP on both of these locations.