With the Knowledge Contributor Role:
Navigate to the knowledge article that you would like to change the author on. Click the Checkout button in the top right hand side of the article.
Once you click Checkout the Author field should be editable. Type in the new authors name and select from the drop down menu.
Click publish.
The article will move to a draft state need to be approved again by the Knowledge Base Manager or Owner, before it is published again.
With the Knowledge Base Manager or Owner Role:
Navigate to the knowledge article that you would like to change the author on.
Click on the article that you would like to change the author on.
You will see that the author field is editable.
Change the author and click save.
From The Knowledge Article List View:
Click on the author field, in the row of the article that you would like to change the author on. A blue box will appear around the author field.
Double click on the box, you will see an Author search box pop-up.
Search for and select the author you would like and click the Save button
Your article will be updated.