Pick up the stitches as for a round neck - mark the stitch that is at the centre of the V. With right side facing you, that is always a 'knit' stitch. On every row decrease one stitch at either side of that central stitch. Continue every row in the same manner until the rib is big enough
Always keep the rib patternn going while decreasing ( I always knit two together through the back of the stitch before the central one and in the front of the stitch after the central one - this is on the row with right side facing you)
Does that make sence to you? Or have I totally confused matters