Try to be perfect! Ok, nobody is perfect. So there are two ways to solve this depending on the type of homework. We assume that you are talking about homework in our learning system (where you watch the videos).
1) You can edit it in our homework (just go to the same lesson and see if you can edit it)
2) Sometimes it is not possible to edit it and in this case you will have to wait until your coach looks at the homework, which he will then reject (since you messed up). You will then have to do the homework again, and can submit the better version. You can work on it while the coaches check your homework.
By the way, typically you don't have to wait more than 24hours for the homework to be corrected.