to add a comment to a photo already posted, open a photo on it's own page. upper right hand corner. two choices - "OPTIONS" or "ADD".
click on "OPTIONS" ..in the drop down menu, click on whatever you wish to do...in this case you want "edit details". click on that option. a page opens with your photo on left side then a box to right of it with the title you posted w the photo. to change from a number to a name etc - click in that box and re-write. under title box is discussion/comment box. to add a descriptive or explanatory note to accompany your photo - click in the box and type whatever note you wish to. then click "save" in lower left side below. when done, it will display your photo as before, but now it will say all the things you wish to accompany it with.