Ftp via router help please

Looking for some help please. I need to upload / update my website, and this is done via ftp.
I used to do this via a bt voyager modem, but it's now broken.

I am trying to ftp with a router, but it does not work. I understand that I have to open port 21, but despite trying to follow instructions from the netgear site and also info from google searches, I just cannot get it to work. I need someone to talk me through it in very simple terms so I can understand what I should be doing.

Win 7 premium 64 bit
Netgear DG834G v3 54Mbps Wireless ADSL router
My website is hosted with legend, and my isp is aol.

Thanks