Ok, the two high strings stay the same (the high E and B). Remove the lower four strings from your guitar.
Now, you open a fresh set of light guage strings and you throw away the two low strings (the low E and A).
You're left with an E string, a B string, a G string, and a D string. These go on in place of your normal G, D, A and E strings as follow:
The new high E string goes in the G position and is tuned up to G (same note as the third fret on the first string).
The new high B string goes in the D position and is tuned up to D (same note as the third fret on the second string).
The new high G string goes in the A position and is tuned up to A.
The new high D string goes in the low E position and is tuned up to E (one octave below the high E string).
There ya go.