To add images/photos to your posts is easy just below the comment box just click one of the three icons choose your file type E.G image/video/link.
The box will then expand and you will see the option to add your files.
Optionally add some text in the comment box and then just click submit.
When adding images you have two choices? Upoload an image from your device or add a url to an image.
To add videos such as youtube etc just click the video icon and paste the url to the video of your choice.
To add a website link click the link icon and add a url.