First, use it for brainstorming. For instance, ask it for plot twists or character backstories. Then, take those ideas and expand on them yourself. Another way is to have it generate a short passage and then rewrite it in your own style. This helps you incorporate its ideas while adding your unique touch.
To effectively use ChatGPT for novel writing, set clear goals. Are you looking for a plot outline? Or maybe character development ideas? Once you know what you need, prompt it accordingly. After getting the output, be critical. Check for logical flow and coherence. Since ChatGPT doesn't always get the 'big picture' of a story, it's up to you to shape it into a coherent narrative. Also, use it sparingly so that your own voice and creativity still dominate the final novel.