The link you referenced is the same video. 5 minutes into the video it references the missing PDF. You have a tab on the link you provided that references static blocks. However, all of the examples reference a different hello theme. Not hello mix.
I know enough about Magento not to even try to see if that code will work.
Could you please either provide a complete set of instructions or verify that the code on the link you provided will work for hello mix even though the code references a different theme.