I don't know about qtcreator, but for kdevelop you must use cmake, which makes things a bit complicated.
You can use codeblocks and then in project options there is an option to link to libraries (make sure you link in both Release and Debug mode). You must add sfml-system, sfml-window, sfml-graphics, sfml-audio and sfml-network (depending on what you are doing).
Or if you want to use kdevelop, you must download FindSFML.cmake (available in the forums), put it into a subdirectory which I'll call cmake_modules (inside your project) and make a CMakeLists.txt that looks something like this:
cmake_minimum_required(VERSION 2.8)
project(nameOfYourProject)
set(CMAKE_BUILD_TYPE Release)
set(CMAKE_MODULE_PATH "${CMAKE_SOURCE_DIR}/cmake_modules")
find_package(SFML 2 COMPONENTS graphics window system audio network REQUIRED)
include_directories(${SFML_INCLUDE_DIRS})
ADD_EXECUTABLE(nameOfYourProject main.cpp someOtherFile.cpp)
target_link_libraries(nameOfYourProject ${SFML_LIBRARIES})