If you want to connect your LG G3 Stylus Android phone with Windows 7 or Windows 8, you will need to download and install the USB driver for G3 Stylus first. For example you want to use your LG G3 Stylus for your 3G modem via USB Tethering mode, this USB driver is needed.
Here we provide the download link for the official USB driver for LG G3 Stylus for Windows 7 and Windows 8. The driver was packaged in .exe file. Double click the file and follow the installation instruction. In case you get the following error, simply click Install this driver software anyway.