Choose the caption bubble to begin. If you want to upload a custom bubble or alternative image then submit the caption first, then edit the comment and attach a "Place img". Once the image is approved you can use it by editing the caption again.
Say hi to Ira and Rebecca (if I got their names right)! They were in Copenhagen on some school trip, but we found out (some earlier than others, eh Toss?) they were already spoken for. Still good company nonetheless.