After installing powercli, when you run the powerCLI shortcut, it calls a ps1 script that adds the snapin.  Running powershell.exe alone does not initialize the snapin by default, unless you've added it to your powershell profile.

The reason the get-vicommand is not working is likely these couple of things:

1. Execution Policy not set to remotesigned (Set-ExecutionPolicy -RemoteSigned)
2. The Snap-In was not initialized (Add-PSsnapin VMware.VimAutomation.Core)