Choosing a server - After logging in you will have to choose a MapleStory Mesos server. If you are planning on playing with friends, make sure you start on the same server as them. Servers are divided into two different rule set categories:
PvE - player vs. player activities are present but restricted to certain areas, and as such this server type is encouraged for new and inexperienced players.
PvP - player vs. player activities are prevalent everywhere in the game world, making life there a lot more challenging - but also a lot more exhilarating!
PvP-RP - these servers employ a rule set that encourages role-playing between players, as well as the rule set used for the regular PvP servers.
Creating a character - Next you will need to create your first character. Here you will choose your character's name, gender, race, class and even appearance. While name, gender and appearance have no impact on game play, choosing a race and class most definitely will.
Your race determines what class you can play, and your class determines what weapons, armor and abilities you can use as well as the general style of game play.
You can read more about races and classes on the official website.