You're doing it right I think, the pattern says - Twist stitches (tw2): Insert right needle into 2nd stitch on left hand needle as if to purl, purl but do not drop the stitch. Purl the first stitch on the left hand needle. Drop both stitches off needle together"
Put the needle into the 2nd st only and purl it, leaving it on the needle. Then purl the first st and you're done, pull both old sts off the Left needle.