I'm assuming you have Wordpress 2.5.1 or higher
1) Go to your wp-admin section i.e.
http://www.yourblog.com/wp-admin2) Once logged in, go to Write>Page and put in your title in the 'Title' text field and your page text in the 'Page' text box

3) You can make it a child page of another parent, but usually you would just put it as a root page, which is default, so don't change the 'Page Parent' at all unless you really want to
4) When you are finished click on 'Publish' and that is it, done - it will now automatically show up on your home page under the PAGES heading in the sidebar.
5) If you choose 'Save' instead of 'Publish' it will save a draft that you can continue working on later on.
6) If you tick the box called 'private' it will make this page only available to you i.e. hidden from the main page to all public users
7) You can then manage (edit) any pages you have published under the Manage>Pages tab whilst still in the Wp-Admin section. If a page is already published and you edit it then just choose 'Save' to save your changes, you don't have to 'Publish' it again.
Hope that helps. That's about as simple as i can get it

Also, make sure you read all my beginner series articles from the beginning as i go through hosting and setting up from scratch

cheers,
Paul.