To add content using the WYSIWYG, log in to the site and select the page you wish to edit.
Click the "Edit" tab to the right of "View."
You should be taken to an editing screen. Select the space where you would like to add content, and select the "Templates" button.
This will pull up a box of Content Templates that you can choose from. Click on the content template that you would like to insert.
Once you add the content template, you will be able to edit. For example, this three-column layout allows you to "Insert content here" for each of the columns.
Save all changes before exiting the page.