All right here are the few steps that you can do

First find the operating system and download it to the usb and make sure to make that usb a bootable usb drive. because if this usb is not bootable then it wont boot up.

second thing is when the laptop just boot up press functions keys(function keys dpends on company) and try to boot up in usb mode. common for this type are f12 or f10 or f2.

so once the usb boot up is set to usb you should be fine.