It's possible to upload images and files for use in your theory page.
Images can be uploaded from the General Options tab above the toolbar. Click the green Add files button to choose the files you want to upload.
Make sure to click the Start button to upload the files.
After the upload, a link will appear that you can use to reference the upload:
Placing images in your theory page
In the toolbar, click the Insert button. Choose Image in the drop-down menu. A pop-up window will appear with some options.
Paste the reference link in the field labelled Source or choose the correct file from the list labelled Image list.
If you want to only display a small image, but you want the student to enable to zoom it, you can set the Dimensions in pixels (or scale with the mouse after inserting the image), and apply the class 'Zoom', also available in the insert/edit image from the editor menu.