Taken straight from PC Gamers website. Hopefully enough people are interested enough that this deserves to be on the front page. If not, I'm sure the mods will move or close it.
You can apply now for a chance to get into the Evolve closed alpha testing session running from October 31 to November 2. The process is simple.
Step 2: fill in the bits and use this when it asks for a "17-character code" - 71687-90535-46031 (More Console Specific Codes Below)
This won't guarantee you access to the four-on-one humans vs. monster shooter as there's limited space, but it's worth a shot.
Seems like everyone can use this one.
Referral Code: EVOLVETOWIN
PS4 Users use this:
It's worth noting if you have both the PS4 and Xbox One, the Xbox One version gets a 24 hour jump on the PS4 and the Evolve Beta is currently only for Xbox One. Who knows if participating in the Alpha helps your chances to get into the Beta, but just something to think about.