when they will send the message to correct the application form

Aishwarya, if this is regarding NEET application form, the correction window will open from January 15th to January 31st. NTA will send you notification only regarding the uploaded images. They might send the notification a day or 2 before the correction window opens. Rest all the details that you need to edit will not be notified. You will have to edit them during the Correction window. As it is just a one time opportunity, make a note of the fields that you need to edit and then once you are done, then click on "Final Submit" option.