To install Active Directory Domain Services or ADDS, Click on the Start button and enter "dcpromo" on the search bar and press enter to execute the program.

After executing dcpromo, this window will appear. Just click next to continue

Click "Create a new domain in a new forest" Since we are going to create new domain and click next

Now, you're going to enter your desired domain name. it can be "css.local", "YOURSURNAME.com" and it can be anything as long as it has extensions such as .com, .org, .edu.

After entering your desired domain name, the system will check if your domain name is valid, not used or available. If so, you can proceed to next step.

After the checking of domain name, You must change the functional level to Windows Server 2008 R2 since we are using that Operating System.

This window is auto-configured and we just need to click next to proceed to the next step

In this window, we need to click the first bullet and then next to proceed.

You can create your own username and password but it is recommended to use the same password as your User account (Server) to prevent any problems.

You don't need to do anything at this point. Press next to continue