What you have to do is shut off main water valve for that area are house and open up toilet valve and take off the big nut, let water drain out of valve. Take nut off stem and replace that washer are get some graffite string packing and rap some clockwise on the stem and put nut back on stem and install it to valve, put it on hand tight as far as you can then open it up a turn and tighten with wrench always keep valve stem free are it will get to tight and you wont be able to turn it. Let me know. If you dont understand then go to http://www.google.com and ask them how to repack a valve on water line.
Art retired plbg