Mitel 5340 SIP password setting via web GUI

I want to run a few Mitel 53xx phones with generic SIP 8.0.04 on my Asterisk PBX. The only way I know to set up the SIPpassword for each phone is via the Web GUI (no option using phone keys). The problem is after I enter the phone ip address in explorer edge web browser, the Mitel Web GUI page does not have the pop-up logon option. The only option on that page is to enter a TFTP ip address. What am I missing? Is there any other way to program these phones other than the Mitel GUI