If I understand your question correctly, you are asking how to ftp to an iSeries and how that command would be used.
The command is used as follows:
ftp ‘xxx.xxx.xxx.xxx’ where xxx.xxx.xxx.xxx is the IP address of the machine you want to ftp into.
The use for such a command is just as its name implies. It is used to transfer files from one machine to another. It can also be used to send commands or start a program which is why most places have it locked down with some sort of security.
As to your second question, the admin will most likely have the telnet command secured in some form or fashion. That means that you will need their permission to telnet into that machine.