Frontiers review is a collaborative process, where authors and reviewers work together to improve the manuscript. Each reviewer might have comments that give a different insight to the work, hence it is important that all reviewers' comments are addressed before submitting any revisions (How can I post a reply in the Review Forum?).
After you have replied to at least one comment from each 'active' reviewer:
Warning: once you start with the process below, all the comments in draft will be posted and become non-editable
Click Resubmit Manuscript
After a confirmation pop-up, you will arrive on the submission form. Modify any desired data clicking on Save when you are done with that part of the form. In particular:
Changes to the author list: for reasons related possible Conflicts of Interest, it is not possible to modify directly the author list when resubmitting. If you need to modify it, please contact the Editorial Office through the "Need Help?" menu in the forum.
Manuscript files: you will need to replace both the Word MS (or LaTeX) version and the pdf version
When you have finished updating the data, go at the bottom to the 'Statement' part of the form and check the box next to the statement on the right. Click on Save and then on Submit.
If resubmission has been successful, the following things should appear in the Review Forum:
Updated Article History: A new entry in the History of the manuscript indicating that you have resubmitted;
View All files: A new row with the new files and the resubmission date.