The offer appeared as a banner ad on Google Play, for me.
Clicking on the banner ad led me to a webpage with "terms & conditions," and stuff like that. Unfortunately, I couldn't cut & paste, for some reason (I took a screen shot, and was going to post it, but then I got concerned about copyright issues. I didn't want our beloved moderator, tubemonkey, to get sued or anything like that.
) So, check your Google Play app (the offer may be on the website, too--I just don't know.)