Hard wire a computer to the device. Open an internet browser and type in the IP Address of the device in your internet browser's address bar. The IP of the device can be found on a sticker somewhere on the bottom or back. Once you type in the correct IP address and hit enter you will be prompted for a user name and password. Most devices have default user names and passwords. Yours should be defaulted to user: Admin, default password: Password. The default information I have given you is assuming you or someone else hasn't changed the user name or password yet on the device. Once logged in you can tweak the settings including SSID of the device by navigating around the GUI.
I do appreciate your response, however there is a flaw in your answer to the question.
Maybe you have a different model Westll than I buy I have a Westell 7500 on my desk as I am typing. There is no IP address on my unit and I don't know of any internet device that supplies the IP address as part of their label information. The IP address is assigned my either, in this case, the DSL/Cable modem to the Access Point connected to it. The access point would then assign an IP address to each device with a communications adapter associated with that device such as an ethernet adapter. What is on the label of my Westell unit is the serial number, WPA code and as all internet devices have the MAC address.
The flaw in my answer was due to the flaw In your question. Good luck.
Sorry, I didn't realize "How do I get into a Westell 7500 menu to change the SSID" was confusing to you.
I have figured it out. Using windows command prompt with the computer hardwired to the Westell 7500 I was able to determine my
default gateway was 10.0.0.1. I entered this gateway address into the browsers address bar and when I pressed enter I got into the menu. So you need the default gateway not the IP address that is not on the bottom of the unit.