If you want to use Xcode, you must install it. Developer tools were bundled into OS X in the early days, but now you must download it, drag the Xcode application into your
/Applications folder, and start it up.
Before you do anything, be sure you can use Xcode 6. There are two considerations.
When Apple brings out a new version of Xcode, it includes software development kits (SDKs) for the latest version of iOS (8) and the versions of OS X that it can run on (Mavericks 10.9 and Yosemite 10.10). In theory, that isn’t much of a constraint: You can still target earlier OSes; the SDK does the right thing to adapt itself to the earlier versions.
However, there are some ...