Community cookbooks are similar to any other cookbook. The only reason it is called community cookbook is because anyone who knows to write cookbooks can join this community and upload their cookbooks to the centralized hub. These cookbooks are available for free and anyone can download and use it. In order to use these community cookbooks, one needs to download them, modify them as per the requirement, and upload them to their respective Chef server.
One needs to have knife configured on their system in order to update, upload, and download the cookbooks. Interact with cookbooks using the knife cookbook commands. With knife cookbook, you can create, delete, show, list, download, and upload cookbooks. Read the knife cookbook commands documentation for more information in Chapter 7.
Following is the link of community cookbooks: https://supermarket.chef.io/cookbooksdirectory