Arcade comes paired with the StarCraft II Starter Edition

If you're already playing StarCraft II, then you have everything you need to skip to step 3 and get started on the Arcade!

1 Create a account if you don't have one already
Create Account
2 Download and install the free Starcraft II Starter Edition
3 Launch StarCraft II and select the Arcade
Launch Game

The FREE Starter Edition of StarCraft II gives you access to the first five missions of the Wings of Liberty single-player campaign, as well as an additional selection of single and multiplayer options. At any time, you can upgrade this Starter Edition to the full version of StarCraft II to unlock twenty-four new single-player missions, two new multiplayer races, and numerous additional units and features.