It means "want to". You can say "I will do as I please" or "Do as you please". It expresses a kind of indifference or carelessness towards the whole situation. If someone won't follow a piece of good advice given with a good intention, the person who gave the advice might be offended and say "Do as you please, then".

It means to do something as they prefer. If I do something however I please, that means I'm doing it exactly how I want, I'm not listening to anyone else, I'm perhaps not being compassionate (ignoring someone's pain), or not listening to advice, but it doesn't have to have those negative connotations. Maybe you just life life however you want, hakuna matata style. Think of it as doing whatever that pleases you. For example I eat the dessert before dinner because I eat how I please in my own house, that is,eating that way pleases me.

Hi, 'Do as you please' is how I would put it.