How do I make macOS the primary boot up drive?

If the MacBook automatically boots up in Windows 10 than, you have to select a different startup disk. Because it may be due the storage issue. So, firstly clean up the disk to having the free space. One can also delete the temporary files and recycle bin folders. call windows 10 help guide for having solution related to it.

To begin with, you need to tidy up the plate having the free space. On the off chance that the MacBook consequently boots up in Windows 10 than, you need to choose an alternate startup circle. Since it might be expected the capacity issue. Simply visit Error 1603 for having arrangement identified with it.

In your Mac's preferences > Start Up Drive select your Mac HD as the Start Up Drive. Save the setting and reboot.