Need help changing boot order ~ Zorin ver 8 installed on iMac
I have searched a lot of places and have been unable to find an answer to this.
I have Zorin ver 8 installed on an iMac. I want to install Zorin 9 and I have it on a CD as well as a USB thumb drive (bootable) My problem is getting the iMac to boot to either the CD or the thumb drive.
I have tried to get into the MAC BIOS by holding down the Windows key, Alt, O & F keys (I don't have a MAC keyboard) but it does not work.
Any ideas/ help would be greatly appreciated.
Thanks in advance!