On the RLC-410W, I was able to upload a certificate as follows.

Connect to the camera's web interface.

Navigate to: Settings / Network Settings / Advanced / HTTPS Settings / Set Up

This will display two file fields: Certificate and Keyfile.

The certificate should be a PEM, Base 64 text file containing the public certificate. The filename must end in ".crt"

The keyfile should be a PEM, Base 64 text file containing the private key. The filename must end in ".key"

You will need a Certification Authority of some sort and might need to convert the files. For example, the Windows certificates manager will not export a private key to the needed format, but OpenSSL can do it.

After successfully uploading the files, close the browser tab to reset the connection.