Log in to the website and click on the "Create content" link on you user account links (under your user name)
Click on the "Page" link (or whichever content type you would like to create)
A "Story" by default has a 'teaser' (usually the first paragraph) automatically shown on the homepage.
A "Page" by default does not get shown on the homepage.
When creating a "Page" or a "Story" you will see the headings TITLE and BODY.
These are both required fields. If you want to make the "Page" or "Story" show up on the primary menu (top right) then you will also need to add "Menu settings".
You can type in your content directly into the editor. If you would like to PASTE content from a Word document then place the cursor at the position that you want to paste the content and click on the middle Paste button on the editor menu.
Once you have a TITLE and BODY content (and if required a menu setting) you may choose to make several options changes.
If you added HTML code into the page BODY (i.e. images or simple HTML) you will need to change the input format to accept HTML. By default it only accepts text.
Click on "Input format" then select the "Full HTML" option.
The other options are pretty self explanatory.
If you what a 'teaser' of your "Page" to show on the homepage then you can click on "Publishing options" and select "Promoted to front page"