With the flash drive connected, press F12 a few times at powerup to open a boot menu.  If the drive is bootable, it will show in the list. If it's not bootable, it will be absent.  Note: you cannot simply copy the install tool to the drive - you must use the "prepare installation media" option to end up with a UEFI-bootable flash drive.  
I wiped my laptop and tried to reinstall Windows 10. It wiped OK then started to reinstall Win 10. During the reinstall, the power went out. Therefore, I am unable to reinstall Win 10 as there is nothing showing when I start the laptop. I downloaded Win 10 installation tool to a USB and tried to restart the laptop to use the tool. I am unable to get it to access the USB to start the installation. How can I resolve this issue and reinstall Win 10.
Inspiron 7548 Windows 10 Reinstall Issue