Overclocking utility should be on the CD. But you could contact them and they could direct you where to get it online. I've had great response via email from their tech support, very helpful and get back usually within the day during the work week.
I'm not big into overclocking and have not on my Biostar board but my board gets great overclocking reviews as being very stable and that the utility works good.
Not sure which version motherboard you have, if it matters.
But checking for my motherboard online I find it here: http://www.biostar-usa.com/app/en-us/mb/driver.php?S_ID=445
Not sure if it would work for yours though. But it is Windows based.