After you log into the BIOS, you can access Secure Boot (enable or disable Secure Boot under Boot) and modify Secure Boot settings (under Security). The key was setting the BIOS password first.
Secure Boot Mode was fixed at Standard. After I erased Secure Boot settings and rebooted, Secure Boot...
Acer machines have a password that must be first set and then entered to obtain access to Secure Boot.
Here are specifics:
https://hub.tcno.co/security/boot/acer/