Every fingering that fits a hand
4321
moderate
4666
moderate
4366
hard · no 5
436x
easy · no 5
What is true of it
Bmaj7 is B, D♯, F♯ and A♯ — 1, 3, 5 and 7 counted from B.
On an instrument that cannot reach all 4, the 5 goes first, in that order.
The easiest of the 4 fingerings below is 4321: 4 fingers, held at the 1st fret.
None of them uses an open string, so this chord moves up the neck unchanged — the same shape 1 fret higher is the chord a semitone above.
Where its notes are on the neck
The brass dots are B, the root. Everything else is a chord tone with its degree printed in it.
With a different note underneath
Bmaj7/D♯
8a79
Bmaj7/A♯
3322
An inversion is the same chord with a different note lowest. The name changes to a slash name because the bass is what a listener hears as the foundation.