I was reading one time, a company was selling keyboard covers so you couldn't see the letters when you looked down. The ability to look down is a big handicap when it comes to learning to type correctly. If you are serious about learning to type, you could purchase a cheap keyboard and scrape off the letters so you would not know which letters are which by looking down. This would probably be cheaper than buying a cover for the keyboard you are using. This would allow you to concentrate on which finger you need to use to get the correct keys while learning where the keys are by touch and not by sight.
One last thing, even though the letters are not visible on the keyboard, you could have a chart printed out somewhere beside the computer. The correct finger placement and keyboard layout for a quick reference would be great until you find you no longer need the chart.