Install.php help needed

I unpacked WordPress and uploaded it with FTP. My hosting provider said to upload it to domains/your_domain/public_html and I did. I edited wp-config.php file and try to open install.php file. If I type http://my_domain.com/wp-admin/install.php in URL box of my browser I get Page not found message. When I tried opening it via control panel I got this weid messed up error message with bunch of code – looking like this http://img266.imageshack.us/img266/4245/wperror.jpg
So I moved all files and folders into domains directory, my_domain directory and even into the directory before the domains directory. Now I have no idea where it should really go and I have even less idea why I get this error message.

Thank you very much for your help in please keep in mind that I’m a total beginner when answering 🙂