In Salesforce, click > Setup. If you are using Salesforce Classic, click Setup located on the upper right pane.
Search for "Package" and go to Installed Packages.
Look for "Jira for Salesforce" and click Configure. You will be asked to generate an API Access Token:
Let's switch over to your Jira instance for a moment so that we can generate a Jira access token.
Now navigate to Jira > Salesforce > Connections.
Choose your Connection, then click on > API Access Token.
If you do not see the above configuration screen, it may be because you are using the Classic Connector for Salesforce & Jira. For Classic Connector documentation, click here.
A pop-up window will appear with your API Access Token.
Copy the API Access Token and paste it in the Salesforce screen from Step 3 and click Save.