Open This Below Link From IOS Device In Safari Browser.
Click On IOS 11, It will automatically download the ios 11 update profile.
Install it and restart you iphone.
After restart go to Settings-General-Software Update-Check For Update.
Download And Install IOS 11 BETA.!!
Compatible Devices :
Note : This Is A Beta Version Of IOS May Have Some Bugs. But i didn't Any Till Now.
It is Running Butter Smooth.
You Can Update to IOS 11 public version later on when Apple Release It Till Then Have Fun With The New Look Of IOS 11.