Once you have downloaded and unzipped the code, open the file index.js in any text editor. Scroll to the bottom of the file, and input your Discord Bot's token into it. (Tutorial on how to get the token here.
Once the token is in, open up terminal and navigate your way to the folder with the code. (Rename the file after you unzip to make it a bit easier).
Run on the terminal npm i discord.js --save then node index.js