"en": How does it work?

Image by Defragged via Flickr1. @ Tex's French Grammar.
a) Read, and listen, about its uses and placement. You should listen to all of the examples. Sure, you can read them just fine, but can you pronounce them as well as you read?
b) Complete the exercise afterwards. There are bound to be words/expressions you don't know, and you will likely miss a word or two (at least) in your answers. So get help from Monsieur Graff and ask why. Tomorrow, then, try this same exercise again. Did you do better?