Switch on the computer and iImmediately press-and-hold the <span class="keycap"b>Option</spanb> key (<b>⌥</b> or <b>Alt</b> key) until a list of possible startup disks appearswhen the startup sound is played.
Choose the USB stick and press <b>Enter</b>. The USB stick appears as an external hard disk and might be labeled <b>EFI Boot</b> or <b>Windows</b> like in the following screenshot: