A dedicated website for the Office of Administration is not available.
Office of Administration
Eisenhower Executive Office Building, 1650 Pennsylvania Avenue, NW., Washington, DC 20503
ESTABLISHMENT AND ORGANIZATION
The origins of the Office of Administration lie in Reorganization Plan No. 1 of 1977, which President James E. Carter prepared and transmitted to the Senate and House of Representatives on July 15 of that same year. The new office was created to "provide components of the Executive Office of the President with such administrative services as the President shall from time to time direct."https://uscode.house.gov/view.xhtml?req=granuleid:USC-prelim-title5a-node84-leaf183&num=0&edition=prelim
On December 12, 1977, President Carter signed Executive Order 12028 and formally established the Office of Administration within the Executive Office of the President. That Executive order was published in the Federal Register on December 14, 1977 (42 FR 62895). Transfers of records, property, personnel, and unexpended balances of appropriations to the Office of Administration became effective on April 1, 1978.https://www.govinfo.gov/content/pkg/FR-1977-12-14/pdf/FR-1977-12-14.pdf
The activities of the Director are subject to the direction or approval of the President. The Director organizes the Office of Administration, employs its staff, contracts for supplies and services, and carries out other duties that the President, as head of the Office, might do. In his or her capacity as the chief administrative officer of the Office, the Director ensures that it provides units within the Executive Office of the President with common administrative support and services.
The Office of Administration is exclusively dedicated to providing uniform administrative support and services to all units that constitute the Executive Office of the President—except for services that are provided primarily in direct support of the President. The Office does, however, upon request, assist the White House Office with providing administrative services that are primarily in direct support of the President (42 FR 62895).
The common administrative support and services that the Office provides fall within the following general administrative areas: personnel management (e.g., equal employment opportunity programs); financial management; data processing; library, records, and information; and office and operations (e.g., graphics, mail, messenger, printing and duplication, procurement, supply, and word processing); and other support or services that can achieve savings and efficiency through centralization (ibid).https://www.govinfo.gov/content/pkg/FR-1977-12-14/pdf/FR-1977-12-14.pdf
Sources of Information
Documents that the Office of Administration published in the Federal Register are accessible online.https://www.federalregister.gov/agencies/administration-office-executive-office-of-the-president