Wow... way to revive this ancient thread. File browser, the thing you use to view the files on your computer... Press the Windows key+E. Now at the top where it tells you "where you are" EX; "My Computer", type in ftp://YourWiisIP
If you're on a Mac or using Linux(I highly doubt this if you don't know what a file browser is) then obviously you can use the Windows key shortcut. A little piece of advice though, if you plan on transferring a large amount of files or just large files for that matter, I highly recommend using an FTP client such as Filezilla.