Hello and thanks for your question.
As of first step, please double check the 1st characters of your Kindle's serial number (B002 or B003)
Press 'Menu' key > 'Settings' - It's the last item on that screen.
Please click this link to download the Kindle update to your computer: https://s3.amazonaws.com/G7G_FirmwareUpdates_WebDownloads/Update_kindle_2.5.8_B003.bin
Connect your Kindle to your PC, open the 'My Computer/My PC' shortcut, and drag the update from your download folder to the drive to which your Kindle is connected (no need to open the device icon).Right click the Kindle's drive and eject. Now Disconnect the USB cable from your Kindle and your computer.Go to the Home screen, press the "Menu" key, and select "Settings.Press the "Menu" key again.Select "Update Your Kindle" from the drop down menu. Your device will restart many times.