If it's a USBTMC instrument (check the manual), then you send commands to it with a VISA Write and get the data back with a VISA Read just as if it was a GPIB instrument. You should read
this to get some basic idea of USB instrument communication. If the USB connection is emulating an RS-232 serial port, then you would use the same VISA Reads and Writes such like you would a normal serial device, If it's not USBTMC or an RS-232, then you could use whatever driver the vendor provides or worse case, USB RAW. Getting the USB RAQ information from the vendor may be difficult though. You should also look at the
Instrument Driver Network to see if a driver already exists for your instrument. Also, anytime you ask about an instrument, it just makes sense to mention the make and model of it. That's important information you need to provide. As far as saving data to file, there a lot of options on your file I/O palette. It's helps to look at the shipping examples.
