Firstly, you need to sit them down and have a conversation, highlighting how important it is that they learn what being responsible is. Secondly, the key to success is persistence and rules that you mutually agreed to beforehand. You need to ensure your kids understand the rules and the fact that they're aware they can now make their own decisions and the consequences of these. Lastly, it is up to you whether you want to tie the allowance to a certain set of chores or educational goals you want them to achieve. Ultimately, just be open to listening, stay consistent and be fair!