I think that you can start your PharmCAS application in July but you can't submit it until August. In the meantime, you should start researching the schools you are interested in to find out whether they are on rolling admissions, whether they accept out of state applicants, whether they require PCAT, whether you can actually picture yourself living there, etc. Narrow your list down because the whole process is very expensive. You can also start brainstorming/writing your personal statement. For most of us, this is what will take the most time and effort and, if executed well, will reap the most benefits. If you can get your PharmCAS application out of the way during the summer, you will give yourself a bit more time to devote to your supplementals/PCAT review during the school year.