For the second time this week, Apple has released an iOS 10.3.2 beta for registered developers only. 3uTools makes fifth iOS 10.3.2 beta available for users testing

Step1: Download and install the latest 3uTools on your PC. Before upgrading, you'd better backup your iDevice. Connect your iPhone to PC with an USB cable. Then head to "Flash & Jailbreak” section in 3uTools → Click "Easy flash". 

Note: If you want to retain the data, please select the option " Retain User's Data While Flashing".

Step2: Select the latest iOS 10.3.2beta 5 on this page, and then click "Flash" button. 

Step3: Keep a good connection between iDevice and PC, and then just wait until this process is finished.