D.C. Mayor Marion Barry yesterday named Annette Samuels, former press assistant to President Carter and a newcomer to his political camp, to be his press secretary.

Samuels, 46, will be responsible for press relations for the mayor as well as disseminating information about city services and programs. She becomes the fifth major spokesman for the mayor during his two years and 10 months in office.

Unlike Barry's previous press secretaries, who either had worked for him during his campaign or had known him as a city councilman, Samuels is just getting acquainted with the mayor. She joins Barry's staff just as the mayor, who has been concerned about his public image, is gearing up to run for reelection.

Samuels said yesterday that she was unaware of her new boss's longstanding dissatisfaction with the way he is portrayed in the media.

"I've just been on the job for a day," Samuels said during a brief interview yesterday. "We really haven't had a chance to work together yet. Mainly I know him through newspaper stories, although we have met socially."

Hired as an assistant press secretary to President Carter in July 1979, Samuels served as a liaison with the nation's "ethnic" press. She has been unemployed since Jan. 20, when the Reagan administration took over.

Samuels also has worked as associate director of public information in the Women's Division of New York Governor Hugh Carey's office. Her other jobs include fashion editor for Essence Magazine, assistant fashion editor for Family Circle Magazine and editor of the Community News Service, a New York City-based organization that provided news about blacks and Hispanics.

"Ms. Samuels brings a wealth of experience to our local government and to me," the mayor said in a statement. "She has been on the forefront of progressive issues for more than 14 years. Her experience at the White House, state level in New York and with a wide array of publications will help me and the District government to communicate to the citizens the wide ranges of services and programs available to them."

Now a year away from the expiration of his term, Barry actively is promoting himself and the city. At construction sites around the city, for instance, he has posted notices that proclaim "D.C. On The Grow."

Morever, city public relations personnel have been put on notice that he expects more "positive" news releases coming from city departments, especially the image-plagued Department of Human Services.

The appointment of Samuels completes a restructuring of the city's communications operation, which the mayor announced in July. It includes the appointment of his longtime aide, Edward M. Meyers, as director of the Office of Communications, the department responsible for dispensing public information on city agencies; the reestablishment of the City Hall New Times, which is the mayoral in-house newspaper; and the announcement of the formation of a Communications Advisory Committee, chaired by public relations consultant Ofield Dukes.

"I look forward to this being an exciting job," said Samuels, who will be earning $32,384 a year as press spokesman. "I find the mayor relaxed, personable and honest."

Barry's first press secretary was Florence Tate, who left amid reports that she was dissatisfied with her limited access to the mayor.

Samuels said she felt that access to the mayor would not be a problem for her.

"I expect that I will meet with him daily -- and sometimes several times a day," Samuels said.