When you're booting your computer, press the appropriate key to open the BIOS or UEFI controls. You'll need to access the boot menu on startup for this to work. Related: How to Boot Your Computer From a Disc or USB Drive

In this case, we want Windows to load the operating system from the USB drive. Once the USB drive with the installation files is inserted into the destination PC, you'll need to set the boot order so that the computer loads the operating system from a location other than its hard drive.