Do you have a question about the Toshiba 40L6353RK and is the answer not in the manual?
Remove AC power, locate the USB port, and insert the USB drive into the TV before starting the upgrade process.
Plug the TV back into AC power to begin the upgrade. Wait for the process to complete and do not unplug power.
After upgrade completion, remove USB, briefly unplug AC power, and then follow on-screen instructions for TV setup.