How Do Chicken Eggs Get Fertilized?

That is why roosters were created.

Through sexual intercourse with a rooster.

Lol, ok,
hens will lay eggs with or without contact with a male, the eggs we buy are unfertilized,
If a chicken has sex with a rooster the egg will be fertalized in much the same way as it is in humans.
It has to be fertilized before it develops it's shell.

Chickens layabout an egg a day.

Really? I mean, this is an actual question? Of course a rooster has to be present to fertilize the hen's eggs. This is how life works. Otherwise it would be like a bunch of virgin Mary chicken births! Read a book! Lol

They have sex

You need a rooster. The roosters mate with the hens and wallah, your eggs are fertilized!