When you have an application form that contains Submission rounds you will see the Round Settings > Submission Form tab as expected.
In rounds 2+ you will see an option Previous Round Field Settings
Previous Round Field Settings Configuration
Once you click this button you will be presented with a list of all fields asked in previous round(s).
If you do not see the field you are looking for choose the Form Page dropdown at the top of the screen.
Then check the Can be edited box next to any field that you wish to allow the user to update.
When the form is loaded, the applicant will be taken to the first visible / editable field they can access.
Limitations / Notes
If the data in a previous round is edited by this setting, the old data will be overridden.
If you are using our Category Groups feature a user can only edit the category field to another category in the same group.