iOS 10 Public Beta Installation
I recommend backing up your device with a Mac or PC before installing the iOS 10 Public Beta, however, it is not required.
On your iOS Device
1. Visit beta.apple.com/profile and install it by following on-screen instructions.
2. Check for updates
3. iOS devices running iOS 8.1.3 or later will automatically receive the latest public beta software over the air. Tap Settings > General > Software Update to install any available beta software.
macOS Sierra Public Beta Installation
2. Scroll down to Step 2 on the macOS Sierra public beta webpage. Copy your redemption code and click "Redeem Code"
3. Enter the redemption code in the Mac App Store window that appears and click "Redeem"
4. Check the Updates tab in the App Store and it should appear.