This stitch is visually not very different from the usual chain stitch. The difference is the direction in which these stitches are done. If chain stitch is done from bottom to top, reverse chain stitch is done form top to bottom.

You would require to know the lazy daisy stitch to be able to start the reverse chain stitch.

reverse chain stitch 1      reverse chain stitch 2
Fig 1: Lay the base for this stitch by doing a lazy daisy stitch, with A as the base point.   Fig 2: Bring the needle out through B. Take the needle under the first lazy daisy stitch without plucking the fabric below. The distance between B and A is just enough to make another chain in the sequence.
reverse chain stitch 3   Fig 3: Take in the needle through B to finish up with the next chain in the sequence. Bring out the needle through C and take it under the second chain without plucking the fabric below.
reverse chain stitch 4   Fig 4: Continue this pattern of stitching to finish the sequence of reverse chain stitch.