How to Deploy Wsp at Central Admin Level ...

1 - Register WSP

Add-SPSolution “WSP Path” -ErrorVariable err -ErrorAction SilentlyContinue  

Ex : Add-SPSolution “C:\CentralLink.wsp” -ErrorVariable err -ErrorAction SilentlyContinue  

2 - Add Solution
Install-SPSolution –Identity 'WSP Name' -GACDeployment

Ex : Install-SPSolution –Identity CentralLink.wsp -GACDeployment

3 - Activate features
Enable-SPFeature "feature ID" -Url "Central Admin URL"

Ex : Enable-SPFeature "8961a1ef-ce95-4e86-bde6-4765644a9b4f" -Url "http://spserver1:2222"