To browse for African History books on the shelves, look under the call number DT.
(A more specific breakdown including call numbers for the history of specific countries can be found in the Library of Congress Classification Outline for DT.)
To browse for African language and literature books on the shelves, use the call number PL:
PL8000-8844 African language and literature
PL8000-8009 Languages
PL8009.5-8014 Literature
To browse for books on Politics in Africa on the shelves, use the call number JQ:
JQ1870-3981 Political institutions and public administration Africa
JS7525-7819.9 Local government. Municipal government Africa