it will fit better after it has stretched a bit (about 10 - 20 miles), but it will fit right away if you just file or grind the edges of the flat tops of the sprocket to go more easily past the rollers of the links
some chains have fatter rollers than others, some sprockets have wider flats at the tops of the teeth - best to adjust sprocket to fit
just had one this week breaking chains & turned out to be that kid has stripped the nut holding the drive sprocket - it wobbled side to side under load - new nut holds it well, but was prepared to replace whole shaft if needed