If you have already bought the game or have the alpha access then be sure to log into the game on Tuesday the 27th of January at 12:00 CET (03:00 PST) .
You can download the game clients here.
But there is also another way how to get to the game. If you will get people buying the game through your referral then you can get another Founder's pack! But it's not for free...
You get Points for bought packs in this way:Pack Points Veteran 3 Epic 5 Legendary 10
and if you want to get new Founder's pack for your friend then you need:Earned Points Number of Packs Pack Tier 15 1 Veteran 25 1 Epic 50 1 Legendary
So for example you must get 1 legendary referral and 1 epic to be able to receive a free Veteran pack.
You can find more details are on the official site.