rpcuser=<username>
rpcpassword=<password>
Don't use rpcuser and rpcpassword, they are deprecated. Instead use rpcauth. A script for generating that is available here:
https://github.com/bitcoin/bitcoin/tree/master/share/rpcuseryes but what does the asterisk on the ip mean?
It means allow any IP address on the range 192.168.1.0 to 192.168.1.255. Of course you should be using your actual IP address that will be making the connection, not your local IP address if you are not on the same local network.
Since you are using a VPS, double check that the VPS provider does not have a firewall blocking the ports that you want. Sometimes they will have an external firewall which you must configure from your account and not on the VPS itself.