First, you have to save the pictures you want to be shown on here to any picture uploading site. (for example photo bucket, tinypic)
After that those sites give you a direct link.
If you want to post this on here you have to use the button " image" (it is the little picture in the frame) and in it you have to enter the link to your image you got from the picture uploading site. After that simply click okay and if all goes well your picture should be shown on here.
Sadly I can't help you with the video part, I don't know how to do this. Maybe someone else could help?