Here we go. In a new reply, you're going to want to hit the + button in the top right corner..
Next, you'll want to hit Attach from Photos
Select the photo(s) you want
Once you do this, it'll start uploading.. Eventually it will say Done Uploading.
Then click on the picture and hit Insert Inline
Hitting that is where the picture will appear in the text, the picture will pop up like this on the reply screen
And then hit send, and it should show up!! Have fun on your honeymoon!!