The forthcoming iOS 9 has a lot of great new features, including the News app, split-screen multitasking on the iPad, transit and walking directions in Maps, new formatting options in Notes, and a more intelligent Siri. For the first time, Apple is making a beta version (which means a not-yet-final test version) available for public download. You can use the new iOS software and report any bugs to Apple. But beware: Apple advises users not to install it on their main device because there may still be some bugs and because some of your favorite apps may not work. If you'd like to give the new software a test run, you can download it by following these steps.
To install the iOS 9 beta on your iPhone or iPad, first go to the Beta Software Program page on Apple's website, click Sign Up, and then sign in with your Apple ID and password.
Then you'll need to agree to the terms before you can enroll your device. You're then taken to the Apple's Beta Guide for Public Betas page, which tells you how to get started, explains how to give feedback, and advises you to back up your device first, so that you can go back to iOS 8 if you need to.
Click on the iOS option at the top. Under the Getting Started heading, you'll see a link that says "enroll your iOS device." Clicking that brings up the Enroll Your Devices page.
This page advises you to do an iTunes backup of your iOS device and then archive it before installing the beta. It then instructs you to go to beta.apple.com/profile via the iPhone or iPad that you want to install iOS 9 on. On that page you'll find a link to download a configuration profile.
Click on that, and then you're automatically taken to settings and an Install Profile window pops up. Then click on Install. This brings up a Consent agreement, which requires that you again click on Install. Clicking on Install brings up yet another window that requires you to click Install.
Then a window appears that says Restart Required. Tap Restart.
Your device then restarts. After it restarts, you're still in iOS 8. In order to install the public beta, you need to follow the same procedure you would with any iOS update: go to Settings > General > Software Update. This will bring up a window that shows iOS 9 Public Beta. Tap on Download and Install.
You'll then need to Agree to terms and conditions, and then tap Agree a second time.
The beta then downloads. Once your iPhone or iPad reboots, you're given 10 seconds to choose to install Later.
If you don't tap it, then the installation begins after 10 seconds. Your device restarts and you're then running iOS 9. But some setup will first be required. Tap Continue, then enter a passcode when prompted, then enter your iCloud ID and password, and then tap Get Started. You'll then be in the Home screen with iOS 9 installed and ready to use.