After you have generated a certificate in Salesforce, you can use it to support two-way authentication for a callout to an HTTP request.
To integrate the certificate with your Apex:
The following example illustrates the last step of the previous procedure. This example assumes that you previously generated a certificate with a Unique Name of DocSampleCert.
HttpRequest req = new HttpRequest(); req.setClientCertificateName('DocSampleCert');