The 6512 is a digital out board. You can search the examples for Digital I/O to see how to set up and work the DIO. This will be used to open and close the valves. Look in the functions palette called NI Measurements - Data Aquisition - Digital I/O. Here you will see built in functions to configure the DIO and write to the DIO. First you configure it, then you write to it to open and close the valves. When done, you clear the DIO to close all the valves.
How is your sensor connected to your test system? Is it RS232, GPIB, other? This makes a big difference. There are examples in Labview on each of these communications methods.