Little dog dominance help?

I've had a black lab mix for a few years now, He's roughly seven years old and he's kind of a softy. Recently (a few days ago) my brother got a smaller dog(its some kind of chihuahua mix). Its incredibly hyper, which is kind of annoying but my main problem is that my first dog is being pushed around by it and i think its trying to dominate him. This annoys me because i like my first dog a lot more than that little rat my brother bought. Is there any way we can teach the chihuahua that Bart( 1st dog) is Alpha compared to him?