You will need to ensure that the laptop has wifi built in, or buy a wifi card to insert into the slot.
You will then need to get a wireless Home Hub from BT, or an ASDL wifi router to plug in, instead of the existing Home Hub, unless that is already a wifi unit.
BT should be able to tell you, but look for a 4" long antenna (cigarette sized) - if you can't see on on the HH, then it's not a wifi one.