Step 1:- Go to CMS - System Management - Public User

Step 2:- Click on “Merge Author

Step 3:- Click on “Add” from the actions column which you want to merge

Step 4:- Select the author with which you want to merge the other author

Step 6:- Then click on the “Merge”  Button

Result - All authors get merged with the selected author and all the articles will get also combined.