I know the feeling!............
This advice is non-specific.............
To enter the BIOS try repeated pressin of Esc. or F2 and there are others (quite a lot) someone else add to the list.
Once there follow the margin prompts to navigate around (no mouse) enter will select and PgUp Or Pg Dn will often work without the arrow keys.
You can back out by using the Esc. key anytime and always have the option to exit save or abandon changes.
In one of the early screens look for something like First Boot Device. Use PgU or PgD to toggle through the alternatives to find CDROM.
If you have a second device choice make it Floppy, and when.... at last the new installation is ready to run, go back and make the HD the bootable choice.