I think you did everything correct, except the path statements. Assuming you have the directories "vnl", "license" and "nlpython" in the directory /home/lxl/software/atk-se/nl/, then you need
export PATH=$PATH:/home/lxl/software/atk-se/nl/nlpython/bin:/home/lxl/software/atk-se/nl/vnl/bin: