In LiveAgent agent panel navigate to Configuration > System > Plugins. Find the 'Jira ServiceDesk Data Migration' plugin and click on 'Activate' button next to it.
Then you have to reload the agent panel. After reload go back to the Plugins section and click on 'Configure' button next to the plugin.
In the configuration popup you have to enter:
1. Jira Servicedesk URL - you have to enter the URL to your Freshdesk account, e.g. https://<DOMAIN>.atlassian.com
2. Username - Jira username (not the email address you use for logging in to Jira)
3. Password - password which you use to log into Jira
In the plugin configuration hit 'Save' and you are done. LiveAgent imports data from Jira in the background.
Here you can see data in Jira:
Jira's data in LiveAgent after importing: