Freeman, welcome to our website and forum. You will need to turn off the water remove the two closet bolts (bolts that hold the toilet to the floor flange) remove the water line from the valve and probably have to replace the water valve as this is the most common item to cause your leak. The new valve will come with a new flange seal; use it. Good luck and let us know how it went.
Looking forwward to reading of your adventures & experiences.
Mike, RVIA & RVSA Certified Master RV Technician
Amy, Dr. Assistant - Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser 450 hp & 1330# torque
06 Saturn Vue, 06 Chevy Z71 4x4 & 2014 Corvette Z51 M7