Apply by sending email at email@example.com or use https://insight.readdle.com webpage. You will receive an email with a link for registration. Proceed to the account set up page and add your Name, email and password. When done just install the client app using the following link: https://insight.readdle.com/i and log in using your account details. Readdle client app is a hub app through which you are able to install Early Access updates.