Hi,
the PXIe-4139 SMU has differential output, so it is the only way to use it.
To use the instrument in LabVIEW, first you have to download the driver available on the following address:
NI-DCPower 18.1
http://www.ni.com/download/ni-dcpower-18.1/7607/en/
After successful installation, you can use the NI-DCPower VIs, that you can find under Measurement I/O » NI-DCPower
I suggest you to look into the examples (in example finder) to get started: Hardare Input and Output » Modular Instruments » NI-DCPower (DC Power Supplies)
ulaci