To use the Scoreloop SDK in your game project, you just need to add the Scoreloop library into your project.
You can add it by going to:
Project properties, under C/C++ build - Settings - Tool Settings - QCC Linker - Libraries. In Libraries(-l), specify scoreloopcore as the libname.
For Cascades applications, you have to modify your application's ".pro" file to include:
LIBS += -lscoreloopcore