There is a description of software installation for all USB devices on site.
 Both USB Voltmeter and USB Thermometer does not need to be installed. Connect the USB Voltmeter or USB Thermometer to your computer and device is able to work immediately.
USB Voltmeter and USB Thermometer are HID devices (human interface device). They use USB drivers already installed in Windows. They work with Windows XP and above.
If the Windows properly recognized USB Voltmeter (USB Thermometer) so the device will appear in the list of HID devices in Hardware Manager.
You can open Device Manager by launching devmgmt.msc : Start - Run - devmgmt.msc 

Screenshot from Device Manager :

USB Frequency counter and USB LC Meter first need to install USB drivers. If were drivers successfully installed, then install USBMeasure software.
Below is describes installation of USB drivers.

For the correct program running you must install USB drivers.This is done only once. Follow the attached screenshots.