You can use a Call Library Function Node to access external C libraries. Include the libraries as additional files in the Source Files page of the Build Specification Properties dialog box. LabVIEW links these files when you build the VI into an application.
If you want to call external libraries from the exported VI, you must create a .dll file that contains the exported function names. Add the .dll file to the Library Name or Path path control in the Call Library Function dialog box.
National Instruments recommends that you do not wire large arrays to or from a Call Library Function Node because large arrays might cause execution delays. To avoid execution delays, split large arrays into smaller arrays and pass them one at a time to or from the Call Library Function Node.