PS
Powershell Tutorial Online

Powershell-with-FileSystem-find-file

Use the Get-ChildItem cmdlet with the -Recurse switch:
Scenario 1:

Get-ChildItem -Path c:\test -Filter File-to-copy.ps1

Scenario 1:
Get-ChildItem -Path c:\powershell-scripts -Filter File-in-subfolder.ps1
Get-ChildItem -Path c:\powershell-scripts -Filter File-in-subfolder.ps1 -Recurse