Educators and researchers are interested in ways that ChatGPT and other generative AI tools might move beyond the role of "cheatbot" and become part of the network of resources students use for writing. We studied how high school students used ChatGPT as a writing support while writing arguments about topics like school mascots. We asked: What did students prompt ChatGPT to do? And how did students take up ChatGPT's responses to those prompts? We used Flower and Hayes' writing model to analyze screencasts of students interacting with ChatGPT and one another as they planned, drafted, and reviewed their arguments. Our data show that while planning and drafting, students primarily asked ChatGPT for ideas and then built upon those ideas to develop their own arguments. While reviewing, they generally used ChatGPT as they might use Grammarly or other editing tools. Students also compared their writing with that of ChatGPT, which allowed them to identify their unique writing voices and build meta-level understandings of rhetorical choices and effects. Our study indicates that ChatGPT can become a part of a social, distributed model of writing, and that students can use ChatGPT as a resource for writing without sidestepping the processes of planning, drafting, and reviewing.