The script is available for download from https://gallery.technet.microsoft.com/FTP-with-SSL-creation-if-ce02c21d.
The sample powershell script does the following:
1. Checks if the required FTP site already exits
2. If it exists it will show the suitable message.
3. If it doesnt exist it will create the IIS FTP website named "testftp" with SSL certificate.
You can find more All-In-One Script Framework script samples at http://aka.ms/onescriptingallery