DO NOT use the in-game camera. It just creates a black box at the bottom of the picture and makes it even more tricky.
1. Press "Print Screen" on your keyboard (PrtSc is sometimes the name on the key)
2. Open an image editing thing and paste the picture.
3. Save it, or you might want to crop the top becaue it will have the zookeeper alerts box still there.
4. Upload it directly to ZA (if you can) or upload it to an image hosting site, and then post the link in [IMG] tags.