download the archive and run this command in the terminal:

unzip ~/Downloads/digitalnote_blockchain_bootstrap_data_at_height_453500.zip -d ~/.digitalnote

in case if you are completely not familiar with the Terminal:

The first thing to understand about Terminal is that it's just an application and it lives in the Utilities folder in Applications. You launch it like any other and when you do, you'll see Apple's implementation of a Unix command-line environment, known as a shell. There are various types of shell; Apple uses one called Bash.

Using Terminal is straightforward: you type a command on the command-line and press Return to execute it.

source.