My fiber optic broadband is installed downstairs and my computer devices are upstairs?

[Thomas]

Quite apart from the obvious "get the engineer back" .....

You need to visit the talk talk website support section. You will need to connect a network cable between your computer and a router, and then you will have to point your browser at the router's web interface. Usually that is something like 192.168.1.1
but it will give all this information on the talk talk website. Once you have access to the router's settings, you will then be able to switch on the wifi.

But you still need to get that engineer back for the telephone!!