You'll get your score on the day you take the test, and most of the applications need self reported scores on the app itself. While you are in the test center you'll be given the opportunity to send the official report to 5 schools. Only problem is that you have to choose whether to do this before you get you're score. The schools don't need your official score on the day you submit your app just your self reported score.
My suggestion would be as follows:
1 - Get started on a couple of apps and read through the forms you need to submit the process will be much clearer after you see exactly what you have to submit, also take a bunch of practice tests. Figure out what your likely score is and then that will help you decide whether send your scores during the test or after. Bear in mind that if you choose not to send your scores on the day of the test it'll cost you $25 per school.
2 - Get started on your essay's, these take wayyyyy longer than you think and are at least as important as your GMAT. Study hard for the GMAT at the same time.
3 - Choose 2 safety schools, 2 competitive schools, and two stretch/dream schools.
4 - Submit apps to one of each type in round 1 and the rest in round two, if you have to retake the GMAT then you might want to hold both of your dream schools back until round 2. A lot of people find that there round 2 apps are of significantly higher quality than their round 1 apps, plus if you get into your competitive or dream schools in round 1 you might save yourself a few hundred dollars.
5 - Chill, this process is a real *complain* and your best bet is to approach it with a clear head and a positive attitude.