I mailed my w2. How do I know the IRS got it?

You mailed in your W2 all by itself?  Or you filed your entire tax return by mail and attached your W2 to the front of the return?

No, I filed with turbo tax. I had to mail it in to IRS because I did not have my tax info from 2015. I printed my return off of turbo tax and mailed it in with all required docs per turbo tax. Thanks.

IRS wont notify you when a paper filed return has been received.   If you didn't put any tracking on the envelope, you'll just have to hope that it arrived.

You can check in on the status of it at the IRS website, you should be able to see when they have began processing it  

I would give it a couple of weeks before expecting it to show up on the IRS website

www.irs.gov/refunds