There are a couple ways of posting pictures and videos to this site.
You can upload pictures to the site by using the instructions in the picture I've attached below (very simple). We also have a Gallery (link is at the top of the site) for any pictures not directly related to your post but you'd like to share.
You can also host or link your picture from another site and use the link in your post. For YouTube videos, simply type or copy and paste (highlight the link and right click or press Ctrl+C to copy & Ctrl+v to paste) the link to the video in your post and it should recognize and embed it automatically.
Enjoy
Chris