Start up your Mac in Windows or macOS
You can set the default operating system, either Windows or macOS, that you use to start up your Mac.
Set the default operating system
Click
in the right side of the taskbar, click the Boot Camp icon 
, then choose Boot Camp Control Panel.If a User Account Control dialog appears, click Yes.
Select the startup disk that has the default operating system you want to use.
If you want to start up using the default operating system now, click Restart. Otherwise, click OK.
You can’t change your startup volume to an external FireWire or USB drive while you’re using Windows. To learn how to change the default operating system using macOS, see Set the default operating system.
Restart in macOS
On all systems: Restart your Mac, then immediately press and hold the Option key. When the Startup Manager window appears, release the Option key, select your macOS startup disk, then press Return.
If you’re using a portable Mac with an external keyboard, make sure you press and hold the Option key on the built-in keyboard.
On non-APFS systems: Click
in the right side of the taskbar, click the Boot Camp icon , then choose Restart in macOS.This also sets the default operating system to macOS.