Hi @Boopathi Subramaniam ,
to install/import a *.nupkg package you can use this:
Install-Package -Name <path-to-the-package>\package.nupkg -Force
To install the Nuget package provider in PowerShell if not already exist run:
Install-PackageProvider -Name NuGet -Force
(If the reply was helpful please don't forget to upvote and/or accept as answer, thank you)
Regards
Andreas Baumgarten