Can i use ready made polenta to make corn bread?

If you mean a package that says polenta to which you have to add water, you can probably use it. The corn meal will be finer than the regular corn meal you would use for corn bread. If your talking the molded prepared polenta that comes in a log, you can't use that. You would be better off buying regular corn meal that has the corn bread recipe on the package or pick up a corn bread mix at your market.