To publish a grouped replacement mission on job boards, you will first need to activate ATS, create a description and/or summary for the specific mission in the grouped replacement window and choose the proper publishing options in the jobboard details
See Jobboard Management section.
Once the ATS has been activated for a mission, this mission will appear in the "Long-term or permanent" section of the Web portal, rather than in the "Temporary" section.
Once you have donne all of the above, just click on Publish job offers in Home ribbon of the main PRIM window.