A. The best way to store a photograph on silk, which is an animal fiber, is flat in a folder made from an unbuffered neutral pH or acid-free paper.
As with all photographs, your treasure should be kept in the dark, and not be exposed to heat and sunlight. Boxes and folders for storing textiles are available through archival products suppliers such as those listed here.
If the piece of fabric is larger than you can comfortably store flat, then consider placing it on a piece of unbleached muslin and rolling it for storage in an acid-free tube. Proper instructions appear in Caring for Your Family Treasures by Jane S. and Richard W. Long (Abrams).
For more information on organizing, digitizing and caring for your family heirlooms, photos and papers, use How to Archive Family Keepsakes by Denise May Levenick (Family Tree Books), available now in Family Tree Shop.