First of all, if you don't have a rooster you aren't getting chicks. And you can't "make" a chicken go broody - it's strictly a hormone thing and as a general rule 2 weeks into laying isn't nearly enough time for her to get all of her egg laying assembly line working without a few kinks along the way.
So I'm afraid that you have a few adjustments to make before your chickens will set eggs. Broodiness is a long process, and a hen can certainly go broody without a rooster, but no chicks will result. You'll know she's broody when she refuses to come off the nest 24/7 and stops laying. But without fertile eggs to sit on, she's just going to make herself sick because she won't be eating much, won't drink as much as she normally would, and will only get off the nest in very short bursts, pooping a huge "broody poop" maybe once a day. A broody hen will sit on anything - apples, golf balls, other hen's eggs, even on an empty nest.
I wouldn't recommend a rooster with only 3 hens....they will be over-mated to the point of danger to them. The rooster/hen ratio is off. If one of your girls does go broody (and again, she doesn't need a rooster for those hormones to get going but she does need him for fertilized eggs) you can find places to buy fertilized eggs to set under her.
Good luck, congrats on those first eggs, and welcome to BYC!