You can use the Image button 
in the editor to insert images, and the media button 
to embed video (as well as Instagram posts, Facebook posts, Tweets etc). Before you can do that, you need to have found and selected an appropriate image, video or other content type that meets our terms of service. Here are some guidelines to help you do that.
Working with Images
Image size
Try to choose images that stay within the image upload criteria. Larger images - especially those that exceed to 4096 x 4096 pixel size - will take longer to upload because they need to be converted to this size. Very large images may take 40 seconds or more to upload.
Intellectual Property and Moral rights
You should try to use image files of photos you have taken, and other images that you have the right to use and share with others.
For example, you might look for images on image services such as Unsplash, Creativity103, Pexels, Pixabay, Encyclopedia of Life, Science Image, or Free Images. Note that some services - e.g. Free Images - also offer you paid images to select from: so take extra care to check you have a free-to-use image. You can also look for Creative Commons licensed images using search tools such as https://search.creativecommons.org/. For example, you might look for images that use one of the following Creative Commons licenses:
CC0 
CC-BY 
CC-BY-SA
In each case, be careful to check you are selecting images that are available for you to use, and ensure you understand the licensing terms. Please check and ensure that you are complying with any license terms for using the image. For example, if the image use requires you to provide an attribution reference to the creator, please make a note in your post crediting the image author. Here are some guidelines on providing attribution.
For more information read about how creative commons licenses work.
Working with Video
The community supports videos from YouTube and Vimeo. Use the media button in the editor to insert videos from those sources, and they will be embedded within your post within a video player.
Embedding content from other Internet services
The community supports embedding content from Instagram, Facebook, Twitter, Flickr, and many others. Use the media button in the editor to insert links to content from one of those sources, and they will be embedded within your post within a preview image.
Image size specs
Content image - topic posts, event posts, group landing pages
- Recommended image width: 704 px
- No limit on image height.
- Image format: png, gif, jpg, and jpeg
- Max file size: 64 MB
Post images
- Post images are the images shared in posts.
- Recommended image width: 714 px
- Max image height: 1071 px
- Image format: png, gif, jpg, and jpeg
- Max file size: 64 MB
User profiles
- User profile images are used in multiple places such as the header of profiles, user teasers, posts, comments, header menu, and the event enrollment block.
- Users can crop the same image differently for different places.
- Recommended image dimensions: 220 x 220 px
- Image format: png, gif, jpg, and jpeg
- Max file size: 64 MB