How to get started with TSG

We have a daughter who is a senior in high school. Just a few months left. (I wish we had discovered TSG earlier). She has a lot of issues. This afternoon we need to meet with the principal because she was talking back at him over a minor infraction. She is very argumentative and very self centered. She also has bad habits, spends a lot of time on her phone, late turning her homework, and does almost no housework (even though she has a lot of time now). She is a smart girls, got into a good college, but obviously, she needs to learn the four basic rules. How can we even get started? With just a few months left?