Starting iMac after installing Windows 10 on Bootcamp (Return to apple starting up first)

I redid / reinstalled bootcamp because i needed a larger Partition. So I decided to upgrade to Windows 10 while I was at it. My question is, when turning on my iMac how do I set priority to booting up the MAC/Apple side. Instead when I turn on my computer, it automatically starts up Windows 10, instead of Apple. Before I upgraded to windows 10 it use to start with Apple and I'd have to press "options" to switch. I'd like to return to that option if it's possible.