You can take a picture of your block and upload it to your camera. I find the easiest way is to scan your block (as long as it's smaller than 8.5x11". Then you get a perfect picture of the block.
When you choose "reply" you get the box to write your message. Below the Send button is the title "File Attachments." You need to know where your picture is on your computer. Click on browse, which will take you to a list of what's on your computer. Navigate from there to where your picture is and double click! Ta da! You can write a title in the long rectangle box if you want.
I find the easiest way to find my pictures is to save them to the desktop. Very easy to find that way. I'm not a Mac user, but there must be an easy place to store things so you can find them quickly.
Good luck!