Keep in mind that any beta version of iOS 10 is liable to be littered with bugs and that many of your apps won’t work properly.  You may decide a taste of the exciting new features is worth it, but we strongly advise against installing the iOS 10 beta on any device you rely on. This warning extends to even the public release of iOS 10, which has suffered from a few problems of its own since its debut.
Backup and archive your data

If you’re going to install iOS 10, make sure you archive an iOS backup. To do that, first make sure you have the latest version of iTunes. If it’s up to date, connect your iOS device to your computer and open iTunes. If you’re interested in backing up your Health and Activity data, select the box called Encrypt [device] back and create a good password. Save this password because there’s no other way to recover the backup without it.

If you don’t want to save your Health and Activity data, just click Back Up Now. Once the backup is complete, head over to iTunes > Preferences > Devices on your computer, control-click the backup you made, and choose Archive to save it.

Now for iOS 10 — to start, you need to check that your device can run iOS 10. Here’s the complete list of iOS devices that support iOS 10.
How to download iOS 10

You can download and install iOS 10 the same way you’ve downloaded previous versions of iOS — either download it over Wi-Fi, or install the update using iTunes. Provided your device can run it, the easier of the two methods is over Wi-Fi. On your device, go to Settings > General > Software Update and the update for iOS 10 (or iOS 10.0.1) should appear.

In iTunes, simply connect your device to your computer, choose your device, then select Summary > Check for Update. If there’s an update available, select Download and Update. For the base version of iOS 10, you need 1.1 GB of free space. If you need to free up space, head to Settings > General > Storage & iCloud Usage > Manage Storage (under Storage, not the option under iCloud).
How to download the public iOS 10 beta

The process to get the iOS 10 beta on your supported device is relatively simple. But first, check if your device is running iOS 8.1.3 or later — you’ll automatically receive the latest public beta software via an over-the-air update if your device matches that version number or is higher. If you want to trigger it manually, just tap Settings > General > Software Update to install it.

If you’re on an older version, the steps are still pretty straightforward. Head over to beta.apple.com/sp/betaprogram to get started. Click on Sign Up and you will be prompted to log in with your Apple ID, or create a new one if you don’t have one. Once signed in, scroll down to Get Started and click on enroll your iOS device.

You will be prompted to archive an iOS backup, like we mentioned above. If you have already done so, all you have to do is go to beta.apple.com/profile on the iOS device you want to install the beta on. You’ll be prompted to install a configuration profile — just tap on Download Profile and  follow the on-screen instructions to complete the installation.

That’s it, you now have the iOS 10 beta on your device!
How to roll back to the current version of iOS

Betas can be unstable, which means it’s understandable if you want to roll back to an earlier version of iOS.

To do this, first make sure that your iTunes is up to date. Then:

    Plug in your iOS device to a computer and open iTunes.
    Press and hold both the Sleep/Wake and Home buttons for at least 10 seconds, and keep holding them when you see the Apple logo until the recovery mode screen appears.
    You’ll see an option to Restore or Update, select Restore. If you had Find My iPhone on, you’ll need to enter your Apple ID and password afterward to activate your device.
    Once complete, iTunes will give you the option to Set up as a new phone, or Restore from this backup. Here, you can choose from any backups you made using an earlier version of iOS.

How developers can download the iOS 10 beta

If you have a developer account with Apple, then you can download the version of the iOS 10 beta the same way, or through the developer website. Go to the Apple Developer website, log in, and download the package. You can use iTunes to back up your data and then install iOS 10 on any supported device.

Alternatively, you can download a Configuration Profile directly to your iOS device and then get the update OTA by going to Settings > General > Software Update.

Whichever method you choose, there’s no limit to the number of devices you can install iOS 10 on, as long as they’re associated with your developer account. To register a device:

    Log into your account on the Apple developer website.
    Click on Certificates, Identifiers & Profiles.
    Look for All under Devices on the left-hand side, and click the addition sign to add your device.
    You’ll need to enter the UDID. You can find it by launching iTunes and connecting your device.
    Find your device in the right-hand pane and reveal the UDID by clicking on Serial Number.