You know what is a Data Flow Diagram, right? If not, look
here.[
^]
LAN Search engine is your product/requirement. You would be aware of how and what of it, thus you would be able to make a DFD of it. Try.
Further, I am not sure how someone can help you in making a DFD via a Forum! After going through online tutorials, if you still need some help then I would suggest you to ask for help from some senior such that you get a better understanding and help in person.