The B minor guitar chord is considered the saddest sounding guitar chord, because it evokes a sad feeling when it's played.
Take a little more time learning this chord; there aren't any short cuts, you'll have to move all four fingers.
When you look at the chord diagram, you'll notice that the B minor is the same as the A minor, except that it is played two frets higher than the open Am chord, with your first finger fretting the high E string at the second fret, and you only play four strings.
Don't get discouraged now, you learned the other chords, you'll learn this one too, and the remaining basic chords are easier to learn!
Try switching back and forth between the G chord and the B minor. Practice this well, because that's a common pattern. Next switch back and forth from C to B minor, D to Bm, A to Bm, E to Bm, and Am to the B minor guitar chord.
Now, play the D chord. Did you notice that you hardly had to think about it? It should be almost automatic by now(if you followed the lessons and exercises from the 1st lesson). Just like the D chord is getting faster to play, and clearer, so will everything else by keeping at it. It gets easier, and easier, and easier! Just play!
It's time to move on to the last of the basic minor chords the D minor.