To add or edit content to your site you need to be in 'Edit mode'. You'll find the switch to enable this mode in the header bar of your site:
If you don't see this switch, click the login link in the top right of the screen.
When in edit mode, bars appear along the top of every content block (we call them widgets). These bars contain an edit button (looks like a pencil) and a place to click-and-drag the widget to a different location on your page (looks like a cross).
Some widgets have an extra option, for example + ADD NEWS ITEM
Adding a new content widget
To add a new content widget, click one of the + ADD CONTENT buttons at the bottom of any column:
A window will appear that lets you choose which type of widget to add:
If you choose a news feed or a results feed, you have options about how many items to show and (for a news feed) whether to show an excerpt and the author and date of the news article.