If you already have children in your family, whether by birth or by adoption, you need to prepare them for a new child joining the family.Initially preparation will be general and take into account it might be a very long time until a new child actually arrives. Once you are matched with a particular child, your preparation can become more specific. Preparation should always be age appropriate.
Below are some links that might give you some ideas as you prepare your child for a new sibling.
https://www.thespruce.com/prepare-child-for-foster-adopted-sibling-27463 https://www.adoptivefamilies.com/parenting/adopting-a-second-child-talking/ http://www.americanadoptions.com/adopt/raising_adopted_and_biological_children http://judymmiller.com/2016/03/preparing-your-child-for-the-arrival-of-their-adopted-sibling/ and a video https://www.kidsinthehouse.com/adoption/support/related-issues/helping-biological-children-accept-adopted-siblings