I have just downloaded the developer Xcode 6 beta. and I couldn't find the settings to set the ios version.
I want to know, How can I run the iOS 7.1 Simulator in Xcode 6.0 Beta?
Finally I found it
Goto Hardware -> Device -> Manage Devices (In Simulator Menu)
or
window -> Devices (In Xcode Menu)
From there you can set the ios version and can add new sim from there.