Second: don't compete with your child's biological parents. Don't try to be better than your stepson or stepdaughter's biological parents. No matter what you think of your child's biological parents, no matter how much you disagree with their parenting style, you should agree and affirm what they have done for their children. You need to remember that no matter how hard you try, no one can cross the blood relationship. Some step-parents always want to heal their children's pain, and this effort may not have a good effect. Stepparents only need to appear in their children's lives, but don't try to "comfort their children's pain" or compete with their biological parents for "who performs better".
Third: Find out what children are interested in. If you happen to be interested in this aspect, you can start to develop a friendship from this aspect. You'd better define yourself as a friend of your child, or an uncle and aunt who cares about your child. In short, don't put yourself in the role of the child's "parents" from the beginning.
Fourth: properly leaving your partner alone with your children can reduce the sense of loss that children feel "replaced". When children can be alone with their biological parents, they will feel that they have not lost their parents' love and are more likely to accept a new family.
Fifth: show love even if you don't like stepsons or stepdaughters. Some couples who have reorganized their families will feel guilty because they don't love their stepsons or stepdaughters. This is normal, just like your stepson or stepdaughter may not love you or even hate you. Accept that you have no feelings for them and don't love them, but you can show them love. When you enter a new working environment, you also know how to be nice to strange colleagues, but you may not have any feelings for them.