Unfortunately, Ragnarok Online 2 is not supported for use with a Mac Operating System. Please read this article
for complete spec requirements for your computer.
There are users who have found ways of running Ragnarok Online 2 on Mac Operating Systems, but these methods are not officially supported and should only be attempted by users who have vast knowledge of their machine's capabilities and who would not be disappointed if they lost their machine if something goes wrong.
There are no current plans to offer support for Ragnarok Online 2 on Mac Operating Systems, however, this may change in the future.