Certification Aid wants to import an encrypted CSV file from the Marketing Cloud Enhanced FTP...

When importing an encrypted file from the Enhanced FTP server, you need to move the file to the Safehouse first, and then decrypt it within the Safehouse.

Move to Safehouse: Use a File Transfer activity to move the encrypted file from the Enhanced FTP server to the Safehouse.

Decrypt in Safehouse: Use another File Transfer activity to decrypt the file within the Safehouse.