To add am image to an email or landing page, click the image icon from the main editor.
Once the editor icon is clicked, you should be presented with a dialog box as shown below.
From this dialog box, you can either reference an external image url, such as from another website. To use such an image, insert the Image URL corresponding text box. If you would like to upload an image, use the icon to the right of the Image URL text box. Clicking this icon will open up a file manager where you can upload a an image file.
From this dialog box, you can upload images, and organize such images in folders. Once the file has been uploaded, you can then click on that image to insert the image into the email or landing page.
Then click Insert. At this point, the image should be displayed in the editor.