President Reagan has named two women in the White House to higher positions. He appointed Kathleen Osborne, his personal secretary, to be special assistant to the president, with the same duties she has had for the past four years. And he promoted Nancy J. Risque from special assistant to deputy assistant to the president for legislative affairs.

Reagan has nominated Rear Adm. Bruce Demars to be deputy chief of naval operations for submarine warfare, investment banker Rockwell Anthony Schnabel of Malibu, Calif., to be ambassador to Finland, former House member Barber B. Conable Jr. (R-N.Y.) to the President's Blue Ribbon Commission on Defense Management and former Treasury Department inspector general John C. Layton to the same position in the Energy Department.

Diego C. Ascensio, U.S. ambassador to Brazil, has been appointed executive director of the Una Chapman Cox Foundation, a nonprofit organization that works to improve the effectiveness of the career foreign service. In February 1980, while ambassador to Colombia, he was among a group of foreign diplomats taken hostage by terrorists and held for 61 days.

Chesapeake Bay Foundation Vice President Charles H. Collins has been named secretary of the board (chief operating officer) of the National Fish and Wildlife Foundation, created by Congress last year to encourage private donations to benefit the U.S. Fish and Wildlife Service and related conservation activities.