How to Upload Certificate in Salesforce Steps to Upload Certificate: 1. Log in to Salesforce and navigate to  Setup . 2. In the Quick Find box, type  External Client App Manager  and select it from the results. 3. Locate and open the relevant External Client App from the list. 4. Navigate to the  Setting  section and click  Edit  then   under  OAuth Settings  locate  Flow Enablement . 5. Click  Upload Files , then browse and select the s erver.crt file. 6. Click Save to apply and confirm the certificate upload.