Yeah, you need to forward the correct ports to your xbox's IP address in your router's settings.
If you want to be able to use the remote control feature via your web browser (HTTP), then use port 80. If you want to be able to access your xbox via FTP, then use port 21.
If you want to be able to use both of these features remotely, then just forward each port separately.
I don't know what type of router you have, but this is pretty much what it should look like on any D-LINK router. I'm sure others aren't too different.
In that picture, I used the IP address of 192.168.0.102, because that is the local IP address of my xbox, so just use whatever your xbox's IP address is.
So basically, what you are doing, is forwarding or transfering any incomming traffic on either port 80 or 21 via TCP to your xbox's IP address at that same port.
I hope that helped you a little,
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Danny