I don't think you can, but depending on your application you probably don't need to. LabVIEW is inherently multi-threaded, so it will automatically run parallel processes in separate threads if it is possible to do so.
Here is a link to an app. note which should help shed some light on the subject:
Using LabVIEW to Create Multithreaded Applications for Maximum Performance and Reliability
Hope this helps you!
