The CMOS hold the current hardware configuration of the computer such that it is stored when the computer is off and is reloaded when turned back on. The error message at the bottom of the screen indicates the information cannot be understood so want you to press F1 to set this up again.
In most cases this is because the battery which maintains the information is flat, supported by the fact that the time has failed as well which although a separate chip is maintained by the same battery.
If you open the computer you should find a silver battery mounted on the board. Normally a CR2032 (20mm diameter 3.2mm thick) these are readily available from shops. The holder does vary but most often a small metal tooth hooked on to one edge is pushed away and it pops, replace the new one with the lettering upwards.
Once done restart the computer and press the F1 key, set the time and F10 to save the default settings is enough to get the computer started.