kDevelop how to build new Package

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Hi,

I´ve used this Tutorial to setup die IDE: http://wiki.ros.org/IDEs#kDevelop" now i have created a new Package via catkin_create and its shown in kDevelop. I´ve added a .cpp in the src folder of the package (containing a hello world source code) but when i build the package i cannot run it

i also added the line "add_executable(hallo src/hallo.cpp)" at the build section in Cmakelist.txt of the package