This article will show you how to add a user to Windows server
Step 1. Right Click on the Windows Icon with and Click on Computer Management

Step 2. Right Click on User under the Local Users and Groups section and click on New Users

Step 3. Insert Username and Password for New user and click Create

Step 4. After Creating the account. New users are shown on the list below

Step 5. If you like to set Administrative privilege to the new user, Click the new user with right button and open on Properties

Step 6. Click on Member Of Tab and then Click on Add

Step 7. Specify Administrators Group like follows
 
Step 8. Make sure Administrators Group is added and then Click Ok