If you're trying to play a chord with 6 strings then you'll need to use one, or more fingers, to cover multiple strings. First, here's a F chord:

e |---1------|
b |---1------|
g |---2------|
d |---3------|
a |---3------|
e |---1------|

On this chord, you'll place your index finger across the neck of the guitar (at the 1st fret).
Then put your index finger onto the 2nd fret, G string.
And, finally, you can either place your ring finger or the D and A string, 3rd fret, or use both your middle and ring fingers to press down those two strings.

Next, here's a B chord:

e |----2-----|
b |----4-----|
g |----4-----|
d |----4-----|
a |----2-----|
e |----------|

With this one you'd place your index finger across the 2nd fret and then either:
1) use your middle finger to hold down the 4th fret (B, G, & D strings).
or
2) use your middle, ring, and index finger to hold those strings down.

I hope that helps answer your question (more than it confuses you anyway). :)