Thanks, achutch, but I think I didn't explain properly -- after I thought about it. The flapper is not leaking as I have turned off the water and the level did not go down. The problem is the "float" mechanism will not stop adding water. It is a slow leak but a leak none the less.
I'll try to get to Lowe's and see if I can get any help, since they obviously carry that brand.
I am reasonably sure I can't afford a plumber but that may be what I have to do. I cannot get the top off the float thing, as was suggested, as it did not seem to "pop off." Not being plumberish, maybe there is some "trick" I don't know.
Thanks for the suggestion and I'll go check with Lowe's to see who is on duty and what they know.