You have to host the image on a web server somewhere. If you do not have a service you can post an image to, perhaps you could post it to a cache log. From there, click the picture icon in the question editor and paste in the link to the picture.
Files have to be treated the same way - drop them on a file server somewhere and click the link button in the question editor. Or simply paste the text directly into the question.
If you have a google account (eg an android phone) or a Microsoft cloud account they provide a server you have put your images/files on. Apple also provide the iDrive with an iTunes account.
