Hey Hiro,
For starters, I'd like to recommend you a Windows VM. That's the easiest to start off with for those new in the server business. If you've got a Windows VM from AWS, you're good to go.
Log into the Windows VM using the remote console or RDP. Then download/copy your emulator files to there. Go into your emulator folder and check the following files:
1) /gameserver/bin/configs/network.properties - forward the port behind: network.port =
Note: don't forward the RMI or database ports, unless you want to risk security by exposing your database!
2) /loginserver/bin/configs/network.properties - forward the port behind: network.port =
For the forward, choose the TCP/UDP combi forward. You'll probably need to forward in two places: the Windows Firewall and the firewall from AWS/your router.
In case you're using the default ports, those are as follows: 8888 (loginserver), 8889 (gameserver), 80 (website), 443 (website).
In the same case, do not forward the following ports: 3306 (MySQL database), 27017 (MongoDB), 9000 (RMI).
I hope this helps you. Good luck with your setup! Let me know if you need any more help.