You can insert graphics into a piece of text by selecting the Graphics tab on the right hand side. This provides a handy preview and URL. You can enter a filename, or a URL from the Internet here. Internet images will be downloaded on the fly, which can minimize the size of your adventure. You can also drag images onto the image preview or filename from a browser.
By default, images will be displayed at the start of the section of text. You can customise where this appears, or insert multiple images, using the <img> tag. The format is
This is useful if, for example, you have <waitkey> or <wait X> tags in your text. Also, you may want different images to appear for different alternate descriptions.
If you wish to hide this tab, you can do this in Settings, removing the tick against Enable Graphics.