That is hard to say, it depends on what browser you are using as some do not support FTP upload. The rule of thumb is to enter as an address ftp://user@host, so in your case ftp://domainname.com@domainname.com with domainname.com replaced with your actual domain name. After hitting enter or go on that you will be prompted for a password, just use you control panel or FTP password.
Now if this doesn't work it just means your browser doesn't support FTP, not a huge problem if you are on windows just open windows explorer and enter the same thing as the file path on the top of the window. This should get the same job done.
If you are on a Mac, or any non-windows computer, you would probably want to download an ftp client, I suggest Filezilla for a good free option, just run a google search for Filezilla and the first option should be the download option.
Hope this helps.
