First you will need to have ComfyUI set up on your system, after that it's just a simple drag and drop. drag the JSON code labled MarkDiffusionV1-55 (https://github.com/markemicek/ComfyUI-SDXL-Workflow/blob/main/MarkDiffusionV1-55.json) into your ComfyUI browser and it will automatically set up!
Here is a great tutorial if you dont have ComfyUI already set up. Once you get to the step that asks you to import a JSON file, you would instead come back to this page and import mine.
ComfyUI Setup Tutorial: https://www.reddit.com/r/StableDiffusion/comments/14sacvt/how_to_use_sdxl_locally_with_comfyui_how_to/