What notes are in the major chord with the root note b

To figure this out you would have to start by writing all the notes in the octave starting with B. BCDEFGAB.  the pattern for all keys are wwhwwwh. w=whole step, and h=halfstep if you have a piano it can be easier to see how the intervals are. a trick to remember the steps between notes are: we walk home when we walk home, or (i think more fun to say) waffle waffle house waffle waffle waffle house.  i hope this helps!