Use the /D switch. mklink /D "Path\To\NewLinkFolder" "Path\To\ExistingFolder"
For those who prefer visual guides, you can find a creating symbolic link in Windows example on the Treehouse community forums. Creating Symlinks via PowerShell windows make symlink
mklink [options] <Link> <Target>
You must run the Command Prompt with administrative privileges unless is enabled in your Windows settings. Use the /D switch