My Wi fi extender worked with BT home hub but now I have changed to Sky it is not picking anything up
will I need the password ?
You won't need the password if your Sky router has a WPS button (if it does, use "Method 1" shown in the user guide on the link I showed above).
If your Sky router doesn't have such a button, then you'll need to use Method 2 which does indeed need the password.
You'll need to check with Sky or the Sky forum if you don't know if your router has a WPS button (it's sometimes called "Wireless" too, and you press it to enable WPS).
Hope this helps.