Ask basic questions a ride iphone environment

There is a mac air on hand, then under what tools should I?
Where under appropriate?

sdk her. . .
Reply:
Register an account at the appstore, then under xcode. . Inside, there's sdk
Reply:
Xcode is the mac OS and iOS integrated development environment.
Directly in the App Store search inside Xcode can download the latest version of Xcode it.
Reply:
Directly in the App Store search inside Xcode can download the latest version of Xcode, after the installation environment will build a good, pre find some video tutorials to see, so get started would be faster. I do have two years of development.