You probably do not have a FTP client installed. Use the package manager and look for 'ftp' or 'ftp client'.
Command not found is either a case of not installed, or not in the path. If you use the package manager to install, the binary files will get installed to standard locations in the path. To see what path is set to, on a konsole run the command 'echo $PATH' and the system will output the curent PATH setting.
Hope this helps.