junosapien
The Choose
option will only show files that have been uploaded directly through the Image Icon > Choose option before. So if you've never uploaded a file through the Image Icon > Upload option then nothing will appear there.
In order to browser your computer's files you will need to click the Upload tab, and click the box to open your local image manager. You can also drag/drop the images into the editor and/or attachment box OR click the attachment box to open your local image manager.
Cheers.