LabVIEW should work with the OS to determine the best location to run any particular thread. By default, each execution system should be configured to have as many threads as CPUs. If you want to modify this, you can click on configure in the threadconfig.vi and select custom system. You can then define the number of threads launched for each execution system. You'll notice one of the choices for number of threads to launch is "n processors". I should note that you will rarely need to change these settings since LabVIEW should handle things well by default.
