Where do you find Emboar in Pokemon white 2?

Answer 1

You can't physically find and catch an Emboar in Pokemon B2W2, and you can only see the pre-evolutions of it in-game if you choose Oshawott at the beginning.

You'll either need to acquire a Tepig or Pignite and evolve it (the GTS is full of Tepigs), or have chosen Snivy as your starter (if you're only after a sighting so you can unlock the Nature Preserve) so your Rival chooses Tepig, eventually evolving it into Emboar. You'd have to delete your save file for that though, so that's a non-factor.

Another thing you could do is use the Unova Link with a Black or White game that chose Snivy as a starter. When you defeat the E4 in B2W2, you can fight Cheren. As you would've used a Snivy in BW, Cheren will have an Emboar to counter it. Again, this is only a sighting gain.

You can also trade one from another game if you raised one in it. Really, it isn't all that difficult to get an Emboar, sighting or otherwise.