where do I put the .gitignore code example

Example 1: git add gitignore

$ touch .gitignore

Example 2: how to use gitignore to ignore a folder

You can ignore entire directories, just by including their paths and putting a / on the end:

1
2
node_modules/
logs/

Example 3: what to add to gitignore

Look at this awesome site!
https://www.toptal.com/developers/gitignore
Generates a gitignore for you, based on the technologies you're using