In Jira Settings → Products → Application Links, create a new link for Salesforce, using the URL of your Salesforce instance (example: https://zcod2020-stg.my.salesforce.com/
Once the link is created, Edit the link to update Incoming Authentication and upload the certificate created in Salesforce
Consumer Key (as shown below) must be the ID of the Salesforce Org which will log into Jira
Paste the certificate downloaded from Salesforce in the Public Key text box (as shown below).
Please make sure to open the certificate in a text editor (with no formatting) and copy/paste the entire content of the cert including the BEGIN–>END brackets.
Save the configuration and close the window