Do you mean B# or Bb?
From your description of fingers, I suggest you mean Bb (Bflat), as B# is the same as C?
Also, Can you confirm which octave? I'll assume you are talking either 1st, or 2nd octave.
There are 2 fingers for Bb ...
-The first uses the Thumb Bb key, First finger left hand, and 4th finger right hand.
-Alternatively, try Thumb Bb key, first finger left hand, first finger right hand.
(Google for flute fingering charts as can explain better than me)
What flutes have you bought, and from where?