Jennifer Myers, an assistant to Greenwich Village artist Marjorie Kouns, helped set up sculpture installations in Washington Sq. Park last weekend for Kounss site-specific public artwork Well-lit Chess Pieces. The sculptures are near the chess tables in the parks southwestern corner. Another part of the installation is large lamp shades that Kouns has put over park lights near the chess tables. Coincidentally, Kouns reports, the chess tables will be the site of a tournament next Saturday at which a grand master is expected to play.