First, find the photo. Second, click on it and press “save photo.” Third, inside the text box of your post across the top line are icons. Look for the icon with mountin peaks and the sun. Fourth, press icon to open it. 5. You will be asked to add a photo by selecting from your own photo library on the Mac. Fifth, select the photo frim your library and choose the size of it you want to post. Sixth, post it here.