Installed Ubuntu now i cant get to BIOS menu

I changed to Ubuntu ,started computer pressed F2 got to BIOS and installed from a USB, but i have been getting to many problems with this, i now have a USB with Windows but now hen i press F2 when starting the computer it does not go to the BIOS menu, i just want to know how to get to the BIOS menu, and why would this happen? I am using Ubuntu 19.04