To reproduce the cultivar you have, it must be done vegetatively...via cuttings. It's a slow process, and there are some special techniques. I've attached just one of many helpful fact sheets that you could find on the internet.

Yes, Camellias produce seeds and they can be collected in the fall as the 'nut' or 'pod' ripens and begins to split. However, any seedlings that may be produced from this method will be as different from parents as are the progeny of any sexual combination.

Here is a link that might be useful: camellia propagation

I would recommend putting air layers on some of the limbs. It is fun and easy, and now is the perfect time of year while the plant is growing. By autumn after it has formed a rootball you cut it off, and voila -- you have a nicely branched plant to place in a pot and let it root out some more before putting in the garden. It will be identical to the parent, and often will bloom the first year. A fellow here made 100 of them on a single plant last year (a large one) and all of them took! Instructions are on the website in the previous post, as well the site listed below which has some pix.

Here is a link that might be useful: Airlayering instructions

A large branch was broken off our camilia with a football!
Is it possible to make new plants out of this please?

Depends how "big" we are talking about. It may be more practical to propagate from smaller cuttings off the big branch.

Here is a link that might be useful: Propagating Camellias

under my camelia bush i noticed 3 little plants coming up that are not attached to the main trunk
how and when do i best move them

It sounds like they are seedlings, in which case you can transplant them when they have a few leaves (3 or 4). By then, if you gently tug them, the roots will resist a little and will have developed enough to move.

You may want to review the article in the link below.

Here is a link that might be useful: Growing Camellias By Seed by SCCS

I cut some branches of different camelia plants and I am planning in propagate. I can dip in root hormones and plant in soil after I cut at the right size ,right? I wonder if I can propagate through the air layers if the branche is not attached to the plant anymore. Is it possible ? What is the best way since the branches are already cut? What size should I have the cuttings ?
Thnks for any help.

Yes, you can dip and then plant.

By definition, air layering requires that the branch being used for propagation purposes remain as part of the main/mother plant. The mother plant will provide nourishment. Once the branch has been cut, it does not receive nourishment from anyone and has to develop roots to survive. At that point, I would dip it into a medium strength root hormone and plant it instead of trying to do air layering. This dip/plant method is called propagation by cuttings and works best if you cut around the fifth node and then leave around 3 leaves. Below is a link courtesy of the American Camellia Society. Have fun, lunanegra.

Luis

Here is a link that might be useful: Propagation by Cuttings by the ACS