The box came with a code that I entered and it said it gave it to me (and my steam account is linked with my vive account) but I don't see it. I dont remember details, this was like a week ago, but I'd assume being it releases in a few hours it would have shown up in my library for download by now wouldn't it?
When you received your Vive box, within the package (buried under some cardboard no doubt) was a card with a code printed on it. When you redeemed that code, you were given a choice between the Fallout 4 VR package and the "All Ages Package"
Once selected, you received a number of content codes you could redeem on Viveport or Steam (according to their source)