Below are all the requirements for delta wifi.com portal:-

Initally you must be a member of the SkyMiles to enjoy free wifi on Delta airlines. So to become a member, you just have to register to their portal.

To get free wifi, you should make sure that you have correct credentials such as username and password.

Be ensure that the web browser that you are using is compatible with the DeltaWifi portal.

Make sure to install the latest version of the browser.