I solved it by myself, the tutorial was probably outdated, all I did was download SFML 2.0, unrar it on my disk, and added this to my .pro file:
INCLUDEPATH += F:/SFML-2.0-rc/include
LIBS += F:\SFML-2.0-rc\lib\sfml-system.lib \
F:\SFML-2.0-rc\lib\sfml-window.lib \
F:\SFML-2.0-rc\lib\sfml-graphics.lib \
F:\SFML-2.0-rc\lib\sfml-audio.lib \
F:\SFML-2.0-rc\lib\sfml-network.lib
I thank you laurent for your fast answer, I solved it in the end