How do you boot Kali linux if it isn't showing up in the boot loader menu?

after installing Kali lunux on a USB and getting it extracted etc. my Acer Aspire E5-575G wont let me access it. Please help asap. or:after installing

after installing Kali lunux on a USB and getting it extracted etc. my Acer Aspire E5-575G won't let me access it. Please help asap.

or:after installing Kali lunux on a USB and getting it extracted etc. my Acer Aspire E5-575G won't let me access it. Please help asap.

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