I believe there is an automatic email when you submit your application that comes with a code and a link to update your application as needed. If you haven't received an email, odds are you didn't tick all the boxes, because you should have.

Also, have you had your application reviewed? That could help depending on your stats. It's not entirely necessary, as I was successful without paying someone to do it, but I did spend a lot of time poring over my application and making sure everything was polished. And by polished, I mean things like the format of phone numbers in your work history are consistent( (123)456-7890 vs. 123-456-7890 vs. 123 456 7890), as one example. I had a fairly long work history to write up and I just copied and pasted the number from google, but that wasn't consistent for every result. It's a lot of data to input, so I just threw it all in and spent some time here and there going back over it to make sure there were no mistakes. I did find small mistakes here and there so it's worth doing.

Also, make sure to periodically update your flight time in the app, and make sure to update your rolling flight time in the past 12 months. My understanding is they like to see updates because that shows consistent interest (though I could be wrong).

Good luck!