Sunday, 11 A.M. to 6 P.M. Sponsored by the mid-Manhattan branch of the N.A.A.C.P. FIFTH AVENUE SUNSET PARK FESTIVAL, 38th to 64th Streets, Sunset Park, Brooklyn.

Lecture on Fat The Greater New York Dietetic Association is sponsoring a free lecture today about fat in the diet and what to do about it from 6 P.M. to 7 P.M. at the mid-Manhattan branch of the New York Public Library, 458 Fifth Avenue, at 40th Street.

When I went to the mid-Manhattan branch of the New York Public Library in November looking for books about Iraq, all I could find to borrow was an account of an 18th-century German's voyage to Yemen.

Or Ann Benton, an art librarian at the mid-Manhattan branch of the New York Public Library.

THELMA GOLDEN is the new director of the Whitney Museum of American Art at Philip Morris, a mid-Manhattan branch of the Upper East Side museum.

Homosexual writers will speak and read from their work at the final events in the "Writers on Writing" series this month at the mid-Manhattan branch of the New York Public Library, Fifth Avenue and 40th Street.

Sunday, 11 A.M. to 6 P.M. Sponsored by the National Association for the Advancement of Colored People (N.A.A.C.P.), mid-Manhattan branch, and the Symphony Space.

Arnold Constable, a retailing name dating from the 19th century, disappeared from Fifth Avenue 12 years ago; where it stood is now the mid-Manhattan branch of the New York Public Library.

Her mother, Alexandra T. Sax, is a senior reference librarian at the mid-Manhattan branch of the New York Public Library.

One afternoon last week, the dominant emotion appeared to be frustration among students and researchers trying out test banks of the new personal computers at the library's mid-Manhattan branch.