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:
[[!img install/inc/screenshots/mac_startup_usb.png link="no" class="screenshot" alt="Screen with the logo of an internal hard disk labeled 'Macintosh HD' and an external hard disk labelled 'Windows' (selected)"]]
Turn on your Mac, then press and hold <strong>Command(⌘)+R</strong> immediately after you see the Apple logo. Your Mac starts up from <a href="https://support.apple.com/kb/HT201314">macOS Recovery</a>.