You can launch ADUC in the same ways that you launch GPMC, through the Start menu or via Server Manager's Tools menu. ADUC is also included in the RSAT tools, so if you have taken the steps to install those on your workstation, this console already exists there as well. Most commonly, I find myself launching these management consoles via Command Prompt, because I tend to always have one up and running on my machine. You are familiar with GPMC.MSC in order to launch the GPMC, but is there a similar command-line shortcut for ADUC? Yes, though you may have to type it in a few times before it gets committed to memory because it's not the most intuitively named MSC:

DSA.MSC—this is the MMC shortcut command that you can launch from Command Prompt, from PowerShell, or from Start | Run. DSA.MSC will open up Active Directory Users and Computers:

We are now looking inside Active Directory. You can see many containers that exist by default here, and some that I have added. OUs, our purpose for visiting this console today, are distinguished by the little icon on top of the folder. While I'm not exactly sure what that little icon is supposed to be, you can see in the previous screenshot that there are many folders/containers displayed, but only Accounting, Accounting Computers, Accounting Users, Domain Controllers, and IT Department have the little extra icon sitting on top of their manila folder. Only these five are OUs.

Creating new OUs or deleting old OUs is extremely simple. Right-clicking on an existing location inside ADUC will present for you a menu from which you can choose Delete to remove an OU, or you can expand the New menu to see all kinds of options. As you can see, there are many more things that can be done here beyond the scope of generating new OUs, but for our purposes you would select New | Organizational Unit:

You can create new OUs directly under your domain, so they reside within this top tier of the domain, or you can create nested OUs by right-clicking on an existing OU (as I have done in my screenshot) and then choosing to create a new OU. In the example provided, when I click on New | Organizational Unit, I would be creating a new nested OU that resides under my Accounting Computers OU.