Choose you client for start the adventure in Supreme RO. Make sure that you patch the client after finishing your installation.
Most modern computers can run Ragnarok Online without any problem. Just in case you’re wondering about the minimum specification required to run the game: your computer must be at least Intel® Core™2 Duo or AMD Phenom II with 2.00 GB of RAM and 10 GB of free space in your storage running on Windows XP, 7, 8, 10.