Enter the administrative settings of my router

I am trying to access my tmobile router to change the SSID name and password as well as turn off a setting that keeps messing up with my  VOIP system , but when i get to the default gateway for the router it doesn’t give a login option like it’s mentioned on this article https://www.t-mobile.com/support/tutorials/device/t-mobile/nokia-5g21-gateway/topic/web-user-interface/how-to-change-the-ssid-name-and-password-gui/3