Salesforce Knowledge is a knowledge base where users can easily create and manage content, known as articles, and quickly find and view the articles they need. After you set up Salesforce Knowledge in your organization, users can write, edit, publish, and archive articles using the Articles Management tab or find and view published articles using the Articles tab. Customers and partners can access articles if Salesforce Knowledge is enabled in the Customer Portal or partner portal. You can also create a public knowledge base so website visitors can view articles.

Articles capture information about your company’s products and services that you want to make available in your knowledge base.

Note:
To implement Salesforce Knowledge at least one Article Type should be present.

Implementation:

1. Go to My Settings.

2. Check Knowledge User check box is checked. If it is not enabled, edit it and enable it.

3. Go to Setup –> Customize –> Knowlede –> Article Types.

4. Click “New Article Type” button.

5. Enter the details and click “Save” button.

6.  Go to Setup –> Customize –> Knowlede –> Settings.

7. Enable Knowledge.

8. Go to all tabs and select “Article Management” tab.

9. Click “New”.

10. Enter the details and click “Ok”.

11. Enter the details and click “Save & Close”.

12. Select the Article and publish it.

13. Go to Customize –> Cases –> Pagelayouts.

14. Edit the pagelayout.

15. Drag and drop Articles related list.

16. Go to Case tab.

17. Click “New”.

18. Save the Case.

19. Click “Find Articles”.

20. Find and attach the article.

Output:

To know about Data Category which is the next step in Salesforce Knowledge, use the below link
https://www.infallibletechie.com/2015/06/data-categories-in-salesforce-knowledge.html