Tutorial: Global field definitions aka blueprint snippets

Hi People,

Is there a small tutorial for the noobs :wink: Or can we (uhm well not me) write one?

How to use the Global field option.

Step 1) add the folder site/blueprints/fields
Step2) made it to step one so far.

Need some help. For example how to (re)use it in your blueprint, and how to set up the yml file.