If you are looking to deploy a WSP using Powershell, use following stsadm alternative commands (PS).

Open SharePoint 2010 Management Shell and type following comman to add solution:

Add-spsolution “C:\installation\mylist.wsp”

To deploy the above WSP, use following command:

Install-spsolution –identity mylist.wsp –gacdeployment

If you want to specify a URL, use following command:

Install-spsolution –identity mylist.wsp –webapplication http://spsite –gacdeployment