Sounds like you are referring to the ServerManager module for PowerShell, not a feature. Modules are managed through your PowerShell profile and your systems environment variables. The ServerManager module for Powershell is not loaded automatically. But, with PowerShell version 3 and later, if you try to run a Server Manager command from Powershell (e.g. Get-WindowsFeature) , PowerShell will load the ServerManager module for you. It will not be persistent though (won't survive a reboot). If it doesn't load automatically, you will need to check your environment variable PSModulePath. If you need the module to be there when you start PowerShell, you will need to modify your PowerShell profile.
To see which modules are loaded in your current session: Get-Module
To load the ServerManager module manually: Import-Module ServerManager
Hope this helps,
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