First you have to capture the photos to the device you are on.
On a desktop that is quite difficult, as AW has protocols in place to stop you, though they can be worked round by going opening the development tools. I'm sure it has been documented in a recent thread.
It is easier on a mobile. On Android if you long press on a photo you are presented with an option to open it in a new tab (Chrome browser). That new tab doesn't have the protections and you can save the image.
Having captured the image you then need to attach it to your post. There was definitely a thread about that recently.