This is a DAQ (Data Acquisition and Control) question, a topic that LabVIEW deals with a lot, and very well. There are numerous discussions and tutorials on NI (and other) Web Sites about NI-DAQmx that you should study (do a Web search for NI DAQ Tutorials).
NI DAQ involves some hardware device to acquire the data and convey it to LabVIEW, typically either over USB or over TCP/IP (including over the Web). The hardware usually provides the "clock", so your LabVIEW code says something like "Acquire N samples at a sampling frequency of F Hz and let me know when you have the data". You typically put this code in a loop, and as the data come in, you plot it, save it to disk, do FFTs on it, or whatever it is you need to worry about. The "Real Time" part is usually handled by your DAQ device, as it (typically) has a very accurate "sampling clock", one that isn't bothered by Windows Updates, Virus Scans, etc., and potentially allows your code to run "as fast as it can", with very little time required by the LabVIEW code to handle the DAQ Task (it mostly "waits" until the data are available).
So learn about DAQmx.
Bob Schor
