Downloading Plug-ins to the host with no account at the host

Hi..

I happened to be an admin of one blog which sitting on a host where I don’t have an account. To install new themes or plug-ins, I have ask the person who owns the host, which seems a bit annoying for both of us. I wonder if you can guide me how to download plug-ins directly to the host computer remotely, without logging into the host computer.

many thanks,
hlee