Because the manuscript may already be under review, changing an already submitted manuscript is normally not possible. You can, however, edit the metadata (for example, add authors).
You can also add material as supplementary files but there is no guarantee that the reviewers (who may already have downloaded the material) see the additional information, unless you do this right away after submission.
If your correction is small we would strongly suggest to wait until the round 1 peer-review is completed and the initial editorial decision email has been received. You can then make the corrections together with submitting the revision (see How do I respond to reviewer comments and upload a revised manuscript?).
If you noticed a major error (for example, an entire section in the manuscript is missing, or you submitted a wrong manuscript version), we recommend to add a supplementary file to your submission (describing it as corrected, final manuscript file for round 1 review), and file a ticket with editorial staff asking to replace the current review version with the supplementary file. Still, we cannot guarantee that the paper hasn't already been reviewed, so the reviewer comments may or may not refer to the old version of the manuscript. Therefore, this should only be used in exceptional cases.
See also:
- How do I respond to reviewer comments and upload a revised manuscript?
- I would like to send a message to the editor about my paper (already submitted).
- Adding Authors to New and Incomplete Submissions
- if your paper is already accepted but not yet published, please see My paper has been accepted but I need to change something/add something/add an acknowledgement/add X/correct Y. How can I do that?
- if your paper is already published, and you wish to publish a correction, see We published a paper in JMIR and have a correction. What is the process of publishing a corrigendum?
- (for staff) How to upload a new review version of a manuscript