You should read the documentation that the error you received refers to. Run the following in PowerShell:
get-help about_signing | more
Once you read and understand that, you will want to execute one of the following:
Set-ExecutionPolicy -ExecutionPolicy Unrestricted
Set-ExecutionPolicy -ExecutionPolicy RemoteSigned
Set-ExecutionPolicy -ExecutionPolicy AllSigned
Don't just go setting it to unrestricted though until you read the documentation in the about_signing help file.
After you have done that, restart PowerShell and your error should have gone away.
--
Kirk Munro [MVP]
Poshoholic
http://poshoholic.com