Peter Pan said:

So what do I need to put on it to stop it from taking over the rest of my
yard?

It's an annual. It will die when it gets cool. You could go to the trouble
of treating it, which will take a couple weeks. Then you'll have this nice,
yellow/brown crap all over your yard for a few weeks until it would have
died anyway.

Next spring, put down a good pre-emergent for it.

--
Eggs

-Half the people you know are below average.