Xcode 7.0.1 and iOS 9.1 are incompatible. You will need to update your version of Xcode via the Mac app store.
If your iOS version is lower then the Xcode version on the other hand, you can change the deployment target for a lower version of iOS by going to the General Settings and under Deployment set your Deployment Target:
Xcode 7.1 does not include iOS 9.2 beta SDK. Upgraded to Xcode to 7.2 beta by downloading it from the Xcode website.