First of all, you will need a free software called PuTTYGen. You can download it here.
Launch PuTTYGen and generate a keypair. Save public key to a TXT file . Open the public key (TXT file) and copy/paste the full contents of it into the user profile in SilverSHielD.
The public key is automatically stored in the server configuration, while the private key is exported (saved) on disk in PuTTY format, thus making it possible to use with every SSH/SFTP client (like WinSCP, for instance).