The drinking age in this province is 19. If you were born after 1999 you will not find anything of interest here for now.
Whether you are shopping for yourself or for a large party, Okanagan offers a wide variety of beer, wine and liqour stores. Mostly, you're stuck buying from your neighbourhood BC Government Liquor Store. There are a couple of places, though that you can buy just beer or wine, often run by the makers themselves, typically a micro-brewery (like the Yaletown Brewing Co.) or one of the many fine BC wineries. You can also get beer & wine at some local hotels. So take the time to find one that has the items you like or is willing to special order them for you.