I don't think you can really "make" them go broody. I tried this spring (April ~ I wanted May babies) and it was a no go. I had a hen that I thought a likely candidate. I put her in a smallish dog kennel covered with a quilt (to make it dark) with fake eggs in it. She was locked in there. Once a day (usually in the morning after the other hens went out), I closed the door to the coop and let her out in the coop for about 20 minutes to eat and drink (and hopefully poop). Then I put her back into the dark kennel for the rest of the day and night. I kept this up for about 8 days. When it became obvious that she wasn't going to go broody, I gave up my "experiment".
Then in mid-July, I had a hen just go broody on her own. I usually collect eggs a couple of times a day. When I went this particular evening, she was sitting tight in the nest box and hissed at me and puffed up. So the next morning, I got the covered litter box (they were using as a nest box through the winter) and fixed it up by the dog kennel. (Boy... that dog cage is coming in handy these days!!) I lifted her up with a towel, moved the eggs into the litter box nest and put her into it. The kennel went in front, with bedding, food and water in it. She didn't come out daily, but was in and out (and did those big stinky dumps) at least 6 - 8 times throughout her 21 day stand. AND NOW I HAVE SIX OF THE CUTEST LITTLE FLUFF BALLS.
All of that to say.... they will go broody when their hormones say to go broody and not before. Apparently some people have had success with the above method. Guess you'd have to try and let us know if it worked!!