iOS is Apple's Operation System for iPod Touch, iPhone, and iPad. I will show step by step on how to upgrade the current iOS to the beta version.
1. Make sure that the iTunes is installed on latest version. If you have older version of iTunes, the latest or beta version of iOS may not be recognized.
2. Search on search engine you prefer (search words: iOS [number: WWDC (It stands for Worldwide Developer Conference) will publish the latest version of iOS] beta download) and download the beta version of iOS after a few hours of WWDC which is held by Apple Inc.
3. Extract the files from downloaded files if necessary.
4. Link the device (iPod Touch, iPhone and/or iPad) on your computer.
5. Open iTunes and it will pop the device you linked. Here is a screenshot:
6. Keep pressing "Shift" key on the keyboard and click the "Check for update". It will pop the window:
7. Click the file which is called ".ipsw" (that means iPod/iPhone/iPad software files.) and "Open"
8. Wait for upgrading
Warning: Because it is beta version, so there are various bugs and it may restart in a few times.9. Done.:) You can enjoy the beta version.