Most YooToob you can simply copy the URL in the address bar at the top of the page and paste it directly into the reply window (not using the link function/"hamburger") and the opening frame of the video displays in your post.
Pics can usually be "hotlinked" by opening the image where it is displayed, right clicking on the image for a menu and select "Copy Image Location" --> paste into the reply window. This leaves the image hosted where you found it and does not have to be resized or hosted here. These links sometimes go dead later on. Sometimes I can restore them, but not always. I post so many images here that I use a hosting site. There are numerous of those, yet what with PhotoBlockit's antics and the fact many of those hosted albums are tracked and can be searched publicly, I only trust ImgZeit. It is secure, simple, and affordable. Plus, I can remember teaching the developer how to ride a bicycle.