Pop-up Editor Images
The Pop-up Editor has its own in-line Image Selector, accessed via an icon on the top right of the toolbar (the one which looks like a mountain).
When you click this icon it opens the Insert/Edit Image screen, shown above. In this editor you can type in an Image Description and an Image Title. More importantly, you can select the image you want by clicking the small icon shwon below (next to the Image URL address) which allows you to browse a navigation screen.
The Navigation screen is used to select an image from the current asset tree, you can navigate up and down in the tree and perform searches. There's also a toggle which switches between a thumbnail image and text name display of the images in the selected folder. Use whichever you find most useful.
When you have selected an image and entered a Description and Caption, click the OK button to drop the image onto your web page and close the editor.