Deploying custom wsp in SharePoint FARM are done in 2 steps - Adding solution, Deploying/Installing solution. These PowerShell commands will work with SharePoint 2010 and SharePoint 2013. For older versions like MOSS 2007, you need to use STSATM commands.
Verify and make sure the account has necessary permissions and SharePoint Management Shell is run as Administrator.
Add solution - Add-SPSolutionAdd the wsp solution package to the SharePoint FARM solution database. This is required before deploying the package.
Add-SPSolution -LiteralPath
Deploy solution - Install-SPSolution
The solution deployment command varies a bit based on the criteria whether it's for a particular web application or all web applications.
The deployment process can be done via Central Admin too.
[Deploy to single Web Application]
Install-SPSolution -Identity -WebApplication
[Deploy to all Web Applications]
Install-SPSolution -Identity -AllWebApplications -GACDeployment
Example
Add-SPSolution -LiteralPath "C:\WSP\Code2CareSolution.wsp"
Install-SPSolution -Identity Code2CareSolution.wsp -WebApplication "http://code2care.org"
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