Toto toilet keeps running. water is going into the pipe continuously.I am stupid about fixing this.....or anything.....any SIMPLE help? thanks

Turn of the feed line for the water. Flush the toilet. Then reach in tank and pick up the flapper valve. Clean around the seat of the flapper valve real well. Check for damage on the flapper valve and clean it as well. Put the flapper valve back in its seat and turn the water on to fill the tank. Then bend the rod for the float down a touch. This will put more pressure on the water valve at the top of the pipe in the tank. If this doesn't work, you may need to change your float valve. They wear out. The ones you buy in the DIY stores generally have diagrams and good instructions for installation.