Refer OAuth 2.0 (3LO) apps (atlassian.com)
Create an app and configure the at Developer console (atlassian.com)
Set the ClientId and ClientSecret site properties.
Use the JQL from Jira's advanced filter and use it to filter the records from Jira on the screen.
In case of custom fields, you might require to update the structure which Outsystems service studio can do it for you.
Code Cleanup