The Theory of Everything was released on November 7th 2014, so you may struggle to find theaters still showing this movie.
I checked my local cinema listings just now, and it was all about Fifty Shades of Grey, American Sniper, and Jupiter Ascending.
Just head on over to www.google.com/movies and you will automatically see film listings for your closest theaters.
Even if it's not showing any more, this looks like a movie worth waiting for on DVD.
I haven't seen it yet either, but through reviews and friend recommendations, I think I've decided that I need to watch this movie too.
Who knows, we might get lucky and it'll get released on Netflix!
Either way, here's the trailer for you to enjoy while you're working out where you can watch The Theory of Everything: