What other "how to's" are important to know with Marketing vs Non-Marketing contacts?

In my HubSpot CRM, how can I assign contacts as marketing vs non-marketing?

1. Ensure your portal is activated for marketing contacts features
2. In contacts, select the applicable contacts using the checkboxes beside each, click the 'more' item in the menu bar above the top of the contact table and select 'Set as non-marketing contact' or visa versa.
   
   
3. You’ll see a dialog box — just enter the number of contacts you’re updating and click ‘Confirm’