Hello everyone I was needing to know how I can successfully replace rotting wood around my toilet. Thank you

You will need to pull toilet, then cut out the rotted portion of floor. Make sure to cut it to the centers of floor joist. If you have access to toilet drain from under floor, it would be best to cut out closet flange, lay new floor, cut new hole for closet flange and reinstall closet flange with a coupling and short piece of pipe(if pvc or abs). Flange should sit on top of new floor and ancher to new floor. Please let me know what type of drain pipe you have.