PoweShell is not installed by default on Windows Core edition. We need to enable the feature. One of the prerequisite for PowerShell is .Net Framework. We need to install .Net framework first:
Command to install .Net Framework 4.0
Dism /Online /Enable-Feature /FeatureName:NetFx4 /All
OR
Dism /Online /Enable-Feature /FeatureName:NetFx4 /All /LimitAccess /Source:X:\sources\sxs
Command to install PowerShell
Dism /Online /Enable-Feature /FeatureName:MicrosoftWindowsPowerShell /All