To change an image right click on an image and select "change image" from the context popup. If you want to insert an image, right click on an image and then click on the insert image icon in the editor toolbar. Highlight and select the text you want to change, and then type over the existing text.

To change a logo, right click on an existing logo and select "change image" from the context popup. If you want to add an additional logo, click next to or on an existing logo and click the insert image icon in the editor toolbar (or the link icon if you want to make an image link to an external website)