how to claim children after a divorce?

kidnap them and go to another country ;)

try use a leash

You have to make your request for custody as part of the initial filing.

see a family law attorney and go to court.

You can't in view of your obvious mental health condition. To quote you: “My pp itch?” and “hitler did nothing wrong”

If you are a female, you just need to cry, exaggerate, and make things up and the courts will side with you. Nobody cares if she is telling the truth, they just want to be the ones who get her to stop crying.

If you are male, you are going to have to prove that your wife is unstable and not competent enough to raise the children. The courts tend to side with women regardless of who is the real breadwinner. You need to talk to a lawyer and see what other options you have.

If you are their parent then why do you now need to claim them? They are already yours.

What do you mean? Claim on taxes? Generally that's covered in the divorce settlement. In some the custodial parent claims them, in others parents take turns (every other year) claiming them.

full custody or partial custody? for full custody you would have to prove your partner is unfit to raise the children.

Partial custody may include only having your kids on weekends or on odd days of the week. you would need to lodge a claim in divorce court and have a very good lawyer, especially if you are a man. Divorce courts do tend to favor women.

In most places you have to formally argue your case in court.  It helps to hire a lawyer.