Simply copy and paste the URL address of the video or image into your question's details or your opinion. After you've submitted your post, the system will embed it for you. Images and videos will only embed in a question's details or in an opinion, never in a question update. Also, you can only post 10 clickable links per post (3 will embed, the rest will appear as links)! If you're wanting to embed your own photo, you'll need to first upload that photo to an image sharing site like imgur or photobucket, then use the link they give you for the image.
Please remember, nothing explicit or offensive! Keep it relatively clean, guys!