The notes of B7sus4 are B, E, F# and A. B is the root, E the fourth, F# the fifth and A the minor seventh. Said aloud, its notes are B, E, F sharp and A.
String by string, low to high, it plays B, E, A, B and F#. Of the five strings you play, two give B, the note that names the chord. It runs from B on string 5 up to F# on string 1.
In B7sus4, only one string rings open, string 2, which gives B. Avoid string 6. Every finger presses at fret 2. There is one more position, starting at fret 7.
Change only string 4 in B7sus4 and you have B7. B7sus4 and D have F# and A in common. Moving to E, you keep two fingers down.
B7sus4 belongs to eight keys. In E major it is the V7sus4, in D major the VI7sus4 and in A major the II7sus4. The rest appear in the key list.