The image will create 3 partitions plus a chunk of blank space when written to your uSD card. One item to note is that you have to remove the µSD card from your Clara HD and mount on your computer. If you are using Windows, it will whine about the card since 2 of the 3 partitions are Linux EXT4 partitions. Do not format the card as Windows suggests. The partition that is exposed when you connect your Clara HD to your computer over USB is a FAT32 partition which Windows can read.
The instructions refer you to the
Memory Upgrade Mod Guide (With Pictures) thread.