Pages are typically created online using the system to display a set of modules laid out on the screen.
Creating a Page
You create a page in the Site Admin area which you can access from any User Preferences box like the one in the top right corner of this page.
Once you are in the Site Admin area navigate to the Pages section by clicking on the Pages tab.
You can either create an empy page or clone an existing page to create a new page with content already in it.
When you clone a page all the modules on the existing page are placed on the new page as well. These are the same modules (not copies) so if you edit them in one page those changes will be visible in the other page too.
Once you have created a page you can add or remove modules and also edit the properties of any modules.
Inserting an existing HTML page
You can also upload an HTML file that you have created on your own computer and make that available as a page of the web site.
First, upload your HTML file.
Then create a new empty page in Page Admin and specify the path to the uploaded file.
eg the url for a file called "myfile.html" uploaded to the events directory of the Orienteering Australia website would be http://www.orienteering.asn.au/events/myfile.html