After you file

Yes, you can. To do so:

1. When you login click 'Take me to my return' (and if you see 'Pick up where I left off' next, click that as well) 
   
2. Next, select the 'File' tab in the top right
3. Click the 'Start' button and in Step #2 you'll be able to make changes

If you need more help please provide additional details.