Luckily, if you've already played Zynga Bingo to level 6, all you have to do is login to your farm to see a pop-up notifying you that your 10 free InstaGrow potions have been added to your gift box. If not, you'll need to play enough Zynga Bingo to level up to level 6 (a task that shouldn't take you anymore than a couple of days to complete) to finally reach that point.
If you're having trouble claiming your free InstaGrows, and you know you've already reached Level 6, you might want to refresh your farm and try again later (we had to refresh a few times before it finally clicked). Just make sure to earn these InstaGrows quickly, as this promotion likely won't last forever!
Have you already earned your 10 free InstaGrows in FarmVille for playing Zynga Bingo? Sound off in the comments.