Just want to write this up in case there are any questions, and this is a fairly unique aspect to Producer fandom too.
For ML2nd, there was a round of in-game lottery for tickets. Same is currently happening for ML3rd. What you need to do is either purchase a BELIEVE MY DRE@M pack or participate in the 11-draw card gasha during the lottery period (until 11/15 Japan time) for an entry code. The entry code can be redeemed on ePlus like the first ML3rd Lottery from the CDs, and you can apply for two events per code, two tickets per application.
If you already play Million Live, I hope all of this is easy to you and you can just do it. If you need instructions on how to get started in Million Live, a free-to-play browser game, you can still consult this old post for some instructions. It should get you far enough to do so. Once you are in the game and past the tutorial, you can buy either the gasha or the BELIEVE MY DRE@M packs without authenticating a phone number. You do need to have paypal or some Japanese point card/GREE coins in order to purchase these items. GREE also takes credit cards, but only for Japanese ones. Just be aware that in-game currency can vary between Android, iOS and web.
Also like ML2nd, a new cool sort of thing that is happening with the in-game lottery is that you can put your name down in the cheering wall for ML3rd. You can think of them like official flower stands. What happened in ML2nd was that for each idol at the two-day event, there was a large board with all the names of Producers who put their names down using the ML2nd lottery pack.
For ML3rd, you can also do the same thing, limited to 1 name per idol per BELIEVE MY DRE@M pack. You do not get to do this using the gasha purchase. This means you can buy only up to 37 BELIEVE MY DRE@M packs maximum.
If you have any questions about all of this please leave a comment!