Apple has launched ios 14.0 beta version , If you want to install ios 14 beta version here is the steps that you need to follow, otherwise you have to wait till july 2020.
Go to apple developer account and login with your credentials . You account should enrolled apple developer account. Here is the link Account.
After that you can see title as “iOS 14 beta” , and download the profile . Just install that profile from your setting of the Iphone.
enjoy!! IOS latest version.