Congratulations on getting your chickens. You have many happy times ahead of you.
Everyone manages their flock in a different way. When I first got my chickens a book said that a backyard flock would most likely NOT need worming. That couldn't have been more wrong. Unfortunately my chickens came with several type of worms.
If your chickens are babies, you may want to consider a worming program. Round worms are the most common type of worms that affect chickens. Unfortunately some things that my chickens love to eat are in the lifecycle of the round worm, such as grasshoppers and even earthworms. Round worm eggs are in the soil and in the bugs that chickens eat. These worm infest the chickens intestines.
Because I live in a climate with no hard freezes, insects never are killed off. It is a climate that insects thrive in.
As a result, I regularly worm my chickens. I worm pullets at about 16 weeks so that anything would be out of their system by the time they lay their first egg. I worm the rest of my flock twice per year.... if I should see any indications of worms I will worm them again at that time. People will state that it is 'hard on a chicken to be wormed' - and I will state that it is probably harder on a chicken to have worms.
Any of these parasites that once infest a flock will have their eggs in the soil or in insects that are around. If you use the bar at the top of the page and type in worming or worm medicine you will probably get hundreds of ideas on worming programs.
My thoughts if you are in a warm climiate, if your chickens eat a lot of grasshoppers, then worm at least once or twice per year.
Last thing. Good for you for being proactive. Your chickens are lucky to have a caring owner.