If you have an account @yorkteaparty.org you can sign in by clicking on the "Sign in" at the bottom of any page.
When you are signed in, if you have edit privileges on this site you will see buttons at the top right of the page like this:
You can
--create another page in this site
--edit this page
--The "more actions" lets you edit site properties and settings.

When you create a page you will have the choice of type of pages like web page, or announcement, for example.

The Web Page template is basically a blank slate in the same style as the site.

When users are signed in on an Announcements page you see a new post button that will let you create a post which will be a new page that will also appear at the top of the Announcements page.  Here in YorkTeaParty.org we have an Announcements page that all registered users can post to. Posts to this page will also show up on the home page in the gadget "Recent Announcements." NOTE: These are the posts that are created when you click on the "New post" button, not the entries into a conversation gadget on the top of that page.




You can also use the Help link at the top right of the page when you are signed in for more information & instructions.

Just like editing any other page, you can insert Images, videos, etc. In fact, it's better to use this insert menu for videos for example because the embed option on the youtube page won't work here but if you copy the URL and then use the insert video from this menu.

Also notice at the bottom of this menu are a few common gadgets and "More gadgets..." which is where you find just about anything you would want to add to your site.