The Skype for Business 2015 package is available for download here: [Link]
You will require 2 machines running Microsoft Windows Server 2012 R2.
Configure the primary domain controller for the FQDN you wish to use for Skype.
Once the system is running and Active Directory has been installed, no further configuration is required on this system.
The second server you will install Skype for Business 2015 prerequisistes using the following Powershell command:
Add-WindowsFeature NET-Framework-Core, RSAT-ADDS, Windows-Identity-Foundation, Web-Server, Web-Static-Content, Web-Default-Doc, Web-Http-Errors, Web-Dir-Browsing, Web-Asp-Net, Web-Net-Ext, Web-ISAPI-Ext, Web-ISAPI-Filter, Web-Http-Logging, Web-Log-Libraries, Web-Request-Monitor, Web-Http-Tracing, Web-Basic-Auth, Web-Windows-Auth, Web-Client-Auth, Web-Filtering, Web-Stat-Compression, Web-Dyn-Compression, NET-WCF-HTTP-Activation45, Web-Asp-Net45, Web-Mgmt-Tools, Web-Scripting-Tools, Web-Mgmt-Compat, Server-Media-Foundation, BITS
Install all Windows Updates, and restart the server.
Log in as the domain administrator.
Mount the Skype for Business 2015 ISO and run setup.exe
 Prepare active directory – run all 3 wizards to prepare your active directory.
 Prepare Skype for Business and install Administrative Tools
 Add the Domain Administrator user to the CSAdministrator and RTCUniversalAdmins groups. This will allow you to publish topology and manage the Skype frontend once running.
 Build Topology and Publish
 Create share folder and assign r/w permissions to Everyone.
 Install Skype for Business – Run all 4 wizards to configure and install skype.
 Generate signed certificates from your cert provider. Ensure that the provider’s root CA is installed in the server’s Trusted Third Party Root Certificate chain. For details, contact your ssl service. Install and assign certificates for Web Frontend and Oauth.
 Start-CsWindowsService in Powershell will run your newly installed Skype server. If anything fails to run, you will have to follow the error code trail to solve the issue. The most common issue is the Certificate chain. Ensure your SSL provider is set up before proceeding with assigning certs. Do not use AD CS to sign certs, it will not allow you to sign in over the internet.