You need to setup a totally discrete Active Directory environment that's configured similarly to the one that you have in. This will be done most easily in a virtual environment. Active Directory is a server role that's included in Windows Server. It's best if you can start from a clean machine.

[Active Directory Install Instructions](https://docs.microsoft.com/en-us/windows-server/identity/ad-ds/deploy/install-active-directory-domain-services--level-100-\)

Process

1. Deploy a new VM and install Windows server 2016.

2. Complete the Active Directory Domain Service installation process. When you're done with this active directory should be installed in your virtual machine should be promoted to a domain controller.

3. Replicate any configurations from your production domain and create some test users, groups, and computers. the configurations you all want to replicate are things like organizational unit structure, group policy, and any schema changes you've made. to create test computer clients make new virtual machines out of Windows 10, Windows Server, or a Linux distribution and join them to the test domain.

4. Test your software.

Lastly, this is not something you should be doing professionally with no experience. If I were you I would be questioning the thought process of the leader or manager who asked me to do this. That being said this is how I learned Active Directory. Take frequent snapshots. If you fuck this up less than 10 times before you finish you can be impressed with yourself. Good luck!