lbou on "Installation - page not found"

Firstly thank you so much for replies!
Do you mean if when I installed wordpress did I fill in details in the / box?? Is that a sub directory? Cos I didn't. Just the dot com website address. I'm sorry if I sound thick. This is a challenge for me as I couldn't even email a year ago!
If it helps, I have followed every step in the tyler moore video 'how to make a wordpress website - AMAZING' published 3rd may 2012 on youtube up until 13.35 min. He comes back at this point after waiting several hours, clicks on the link and it works for him but not for me!
Please let me know if I can give you any more details and I do apologise for my amateur level of competence!