Unlike the CMD.EXE CHDIR or CD command, the PowerShell Set-Location cmdlet will change drive and directory, both. Get-Help Set-Location -Full will get you more detailed information on Set-Location, but the basic usage would be
PS C:> Set-Location -Path Q:MyDir
PS Q:MyDir>
By default in PowerShell, CD and CHDIR are alias for Set-Location.
(Asad reminded me in the comments that if the path contains spaces, it must be enclosed in quotes.)
To go directly to that folder, you can use the Set-Location cmdlet or cd alias:
Set-Location “Q:My Test Folder”