Once you are logged in to your Wunderite instance (app.Wunderite.com), you will see the "Task" list dashboard. From here, you will select "Show Completed Tasks".
Once you select "Show Completed Tasks", all forms you have previously marked complete will show up. You will select the form you would like to go back and edit by simply selecting the form or selecting "view".
Once in the form, there will be two areas in which you can select to unlock the form, both labeled "Edit Answers". One will be in the top left dashboard, and one at the bottom of the form if you scroll all the way down.
After selecting one of these "Edit Answers" buttons, the form will unlock and you can edit or add any missing information. Make sure you mark the form complete when you are complete again, to notify your agent!