Replaced cmos battery in OptiPlex 745, now just black screen - no option to reset BIOS

One frustrating issue is that no one knows the key to hold down upon startup. Some say F2, some F12, some F10, and some the Delete Key. This is a specific machine OptiPlex 745. I don't understand why it is so difficult to find that info. I looked in the available .pdf user manual. If it's there, I missed it. Most how to do it videos and text descriptions start with entering the BIOS. But I can't get that far. The monitor is plugged into the non-VGA port. I'll look for a VGA but I think it just has this other port and a serial port (along with USB's and ethernet). Some help posts said the mothe

Question by Paul on Super User, licensed CC BY-SA. We show a short excerpt and link to the original thread as credit.