You can use VISA in LabVIEW to communicate over your RS232 port. RS232 has a transmit line, and a receive line that are both referenced to ground. These three lines are all you really need to use if you want to send and receive data.
I'm not familiar with that FPGA, but once you send your data from your FPGA's RS232 port you can read it back in LabVIEW by specifying the number of bytes to read in a VISA Read.
Shawn B.
National Instruments