Have a read of this :-
@russell986 if you have started the 7 day Boost Trial online, then it may take 4 hours to trigger, should you sign out and back in on your device the Boost Membership should start straight away.
If you are a BT TV customer then to get two streams at the same time you will need to follow the start up sequence on this BT Guide under "Streaming and Devices ".
To amplify what @schnapps says, ‘with BT’ for the purpose of getting two simultaneous streams means that you must be subscribed to BT TV, and to Now through BT TV.
I am ‘with BT’ in that BT is my ISP; but I don’t subscribe to BT TV, and I certainly don’t subscribe to Now that way, preferring the flexibility of the constant automatic Retention discounts that Now ply me with every time I start the Cancel process 😛