When you first log onto your site with ftp you are in the home directory. You should see a directory with your domain name. This is where all files go that are to be seen on the web. The main page (first page) in that directory is called index.html (the extention can also be .htm) or index.php if you are using php programming.
Once this index page is uploaded into that directory, you should see that file, with a web browser pointed at your domain. (ex. www.example.com)
If you still can not see it it may be possible that the domain is too new. Meaning that the domain name is not done propagating across the internet. In this case you must wait awhile until it is done, then the web page will be excessable.
Hope this helps