Yea the application opens in May (to fill it out) and you can submit it like June 5th or something. I believe you can do the AACOMAS fee waiver in April. If you do it before then then they will count it towards this current cycle. I think I might have even waited until the beginning of May because when I emailed them about it, they were not giving good answers. I think so long as you do it some time within a couple weeks before submitting then you are good to go.
***Side note, make sure you 100% tell the schools that you are applying to that you have the waiver BEFORE sending back your secondary to them. I lost like $800 total because I naturally sent my secondaries back super fast and then when I asked about reimbursement they told me I had to tell them before hand. Each school does it differently so you have to contact each one individually as you receive secondaries. Just thought I should add that since no one had explained it to me. But for your primary app, so long as AACOMAS has given you the thumbs up on your waiver then they will automatically take off the price of the 3 schools or whatever it is, you dont have to do anything special with it.
Please feel free to personal message me any time over these next few months if you have any questions or concerns, I am happy to help out.