In your web browser go to
http://192.168.1.1/ and you will see the LogIn screen that the modem software produces. You don't even need the modem to be plugged in to the telephone line to do this. That screen is produced by the modem software inside the unit.
You need to log in to the modem Admin screen using the user name admin and the password admin, and click OK.
Click on Basic and then on WAN, and then on the pencil icon at the top right of the screen.
Make sure that VPI/VCI is set to 0/38 and that PPPoA mode is selected as well as VCMux being selected.
Make sure that you correctly enter your Broadband user name (like
02087654321@talktalk.net) and password (like a1b2c3d4) in the appropriate boxes on that screen. Those will be found in the letter that you received from TalkTalk and they can also be got from an automated system on the TalkTalk customer service line if you ring from your own phone line.
Finally, make sure that you click Submit and then on Save All and then OK. This then stores your broadband user name and password inside the modem.
As soon as you connect the unit to the telephone line, the unit will then dial out and connect to broadband, supplying your user name and password automatically for you. There is an inbuilt statistics page where you can see what is happening, and some in-built diagnostics too.