Each photo or video sharing site will have specific code to paste for this feature to work.     

Embedding Instructions

1. While editing a post, create a custom field with key HTML1 and paste the code you want to embed into the Value field.
2. In your post write HTML1 with brackets around it [ ] where you want to embed the html code. (Use the standard wysiwyg post content editing window, no need to switch to Code view).
3. If you need, you can use up to nine times the trick: HTML2…HTML9 in order to embed up to nine html different snippets per post, placing each snippet in a different custom field

Sample 1:

Sample 2:

Sample 3: