In general, the first boot of the computer is the optical drive, but sometimes we need to change the startup items, this tutorial for you to introduce how to set the USB as the first startup items, the following look at the specific settings.
First of all
In the boot press del or F2 or F12 or ESC to enter the BIOS settings, specifically look at the start of the prompt
The most common phoenix-award bios option is to select Advancedbios after entering features
Change the device to Usb-zip or USB-HDD
After the change, press F10 to save the exit
BIOS tuning options for Dell-branded machines
BIOS for ThinkPad Series notebooks
BIOS for HP Commercial Notebook series
Acer notebook settings options: Switch to the boot,↑↓ key to select USB-HDD, press F5 switch to the top
You can see that all of the BIOS options are different, but the adjustment options are for one purpose: Set the computer's startup to boot from the USB device, so that you can start the computer from the U disk.