Private/Public key encryption and digital certificates

Hi All

I am looking for someone with in depth knowledge of this process.
I have a req. to make my app communicate with a secure server.
The process should start by creating a digital certificate and sending a request to sign the certificate.
Afterwards all messages sent to the server should be signed for authenticity.

Anyone with in depth expertise in this, please PM and so we can discuss.

Thanks
iCAB