KDevelop uses cmake, just add to your CMakeFiles.txt:
target_link_libraries(
your_target_name
-lsfml-graphics
-lsfml-window
-lsfml-system
OR, if you installed the FindSFML.cmake script,
find_package(SFML REQUIRED COMPONENTS SYSTEM WINDOW GRAPHICS)
...
target_link_libraries(your_target_name {SFML_LIBRARIES})