The Bm barre

Bm is the 5 of E minor, and the one chord of the key that won't play in the open position. Its shape is your Am, moved up two frets, exactly like the G minor scale was E minor moved up three. Your first finger lies across the strings at the 2nd fret and does the job the open strings did.

Barres are hard. Most players take weeks before every string rings, and it hurts a little at first. That's normal. Keep the first finger straight and close to the fret, roll it slightly onto its bony side, and let the arm's weight do the pressing rather than squeezing with the thumb.