Just go to the full reply screen, then you have two options. If the photo is archived in an online cloud, you can then click on the Enter The Image Icon on the tool bar and paste the link which will do the job.
If you have the photo in your PC, click on the file manager at the bottom of the page, then click Browse, select the file from your PC, click Open, finally, click on add file.
Hope this helps,
PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!
K+E=W (Knowledge Plus Experience = Wisdom.)