There's no iWeb for the iPhone, you need a Mac.
If you'd like to have an overview on how iWeb works before you start the learning by doing process visit the website of my friend Roddyhttp://www.iwebformusicians.com/WebMusic/WhyiWeb.html
and keep clicking on the Next Page button at the end of the pages.
Roddy kind of guides you through the process. His site is made for musicians in particular but is also really useful for non-musicians to get started.
If after you visited Roddy's site and read my FAQs you still have questions you're always welcome.