Changing resolution in BIOS

When I boot up, the display resolution (font size)  on the welcome screen is very small.   When I try to change the resolution in display, it doesn't have any effect on the welcome screen and I can't seem to change the resolution in some of my programs.  I'm not familiar with how to make changes in BIOS, but can someone provide a step by step on how to make changes in BIOS that will correct this problem.  Thanks for any help.  Ro Lord