That's SFTP, not FTPS.

Anyway, start here:
https://winscp.net/eng/docs/faq_script_modified_files
https://winscp.net/eng/docs/guide_automation#results
https://winscp.net/eng/docs/script_email

thanks Martin

I am able to connect to FTPS using -privatekey and command link interface

Next step is to download any new file in the remote directory (filename_xxxx.csv) to local directory....and write to a log file and send a status mail alert to specific email id.
can you help with this ?

Thanks

SFTP does not use client certificates.
So either you mean private key (used with SFTP/SSH).
Or you mean FTPS (which uses TLS/SSL and hence the certificates).

For private key, use the -privatekey switch.
For client certificate, use the -clientcert switch.
https://winscp.net/eng/docs/scriptcommand_open

In any case, you have have the GUI generate the script for you:
https://winscp.net/eng/docs/ui_generateurl#script

I am working on a script which will automate the downloading of files from remote sftp server.
The issue is certificate authentication
Right now I am using WinSCP GUI and in the Advanced settings of the WinSCP session with remote server I have supplied the SSL certificate.
WinSCP connects to remote server using this certificate and once sessions is established I go to a remote directory and copy a file to local directory.
I need to automate this and schedule it so that in every 30 minutes the script is run and if a new file is copied to remote server directory, it will be copied to the local directory.
I have one script which works fine for FTP but for SFTP with certificate I need help in creating a script which can be used to connect to remote SFTP server passing on certificate authentication and download the file.

Thanks
Gautam