Once you click on the [New Content] button on your edit page content screen in the work area you will see this:

For most new page content all you have to do is select  Regular text element.

Below are screen shots of all the options that you will see on your screen.

At the bottom of the screen you see 2: SELECT POSITION:

Here you can see the other page content sections and choose where you want to place the new page content.

If you have been instructed by the web designer that you can use the 'Left', 'Right' or 'Border' position also rather than only the Normal position, here is the place where you make that choice.

All you have to do is click on the grey arrow next to the grey folder and your new content will be placed there.

Now all you have to do is write your text in your newly created content section.