plugins and WordPress.com help!

I’m a novice which doesn’t help. I use wordpress.com – I’m trying to build a simple site.

Someone said I could use a ww.wp.xz.cn plugin to make a nice widget for a mailing list on my home page.

But when I go to this link http://ww.wp.xz.cn/extend/plugins/mailchimp/installation/

and look at the wordpress plugin – I can’t even figure out how to start! I download one version – but have no idea what to do with it.

Any (simple) advice?