To make yourself admin, you need to assign the Admin rank to yourself. Write this command in the server's console: "rank <yourname> Admin" (note that the command is case-sensitive)
The server will use any IP address that your computer has, there is no need to explicitly set the address anywhere. If you have no router / NAT, then the server will be accessible from the internet without any further setup. Your friends will need to know your IP address, though, because that's what they will use for connecting.
So you can use "localhost" to connect to your server, your friends will need to use "<ip>"; this IP may change, you can find the current value using the "ipconfig /all" command on Windows, or "ifconfig" command on Linux.
The server will use any IP address that your computer has, there is no need to explicitly set the address anywhere. If you have no router / NAT, then the server will be accessible from the internet without any further setup. Your friends will need to know your IP address, though, because that's what they will use for connecting.
So you can use "localhost" to connect to your server, your friends will need to use "<ip>"; this IP may change, you can find the current value using the "ipconfig /all" command on Windows, or "ifconfig" command on Linux.