I only ever do it from the laptop, when if making a post there is an image button.  I click that then copy/paste the image URL within the boxes that come up.  You get great Coyne/Greengrass photos on google image search IMO

I do this for gifs too, which again, I get via Google image search.

As for personally taken photos, I upload them to imgur and copy/paste in the same way as above.

For youtube videos I just copy/paste the URL without clicking any button first.