Choral music is more harmonic than melodic. The basic idea, in my opinion, is that dissonance creates tension, and consonance relieves it. How to enjoy it? At every moment, try to figure out if you're liking what you're listening to, or if you're not, and why exactly that is. Observe yourself reacting to the music, rather than just the music. That's how I got into classical music, and it may not work for everyone...
EDIT: Also, there is no "proper" way of listening. What's important is that you figure out what exactly you like or not.