Unable to intall BIOS update

For pending upgrade been advised to update BIOS

This is on a Dimension E521  BIOS 1.1.4

I have downloaded the new BIOS   file: DME521-010111      I put in on an empty USB stick  ..... checked USB stick can be read and file is visible.

Went into BIOS and checked
'on board devices' > USB controller = ON

'front USB' = ON

Then did a restart to boot menu with F12

It gives option to boot to 'USB-ZIP'

I select that ... screen blanks ... then after a pause I get message on screen:

Remove disks or other media

Press any key to restart

If I press any key. just get same message at each key press.

Do I need to make USB bootable ? .... I did a little googling and came across an article that said to use CMD prompt and DISKPART

However couldn't proceed as when I used list disk

it only shows HDD not the USB so could not proceed

Do I need to make it bootable ? .... if so is there another way