adding a pic out of your group (groups) albums is done pretty much the same way...
click on this icon on your reply
it will open the same web page dialog box.
go to the "my online photos" tab this time..
when you click on it your list of groups will appear on the left side..
pick the group.. click on it
pick the album.. click on it
wait till it fully loads..
click on the pic you'd like to insert.. (it should now have a red frame around it)
click add photo..