What model IBM is it? Some older IBM's (eg. ps2/system 70) don't have a
setup program built in ,they instead use a "reference disk" which you can
download from IBM's site.
For the IBM PS/VP series (their "clones"), you press F10 when you see
a little "icon" (a rectangle with a few squiggles in it) in the upper
right hand corner of the boot up screen. This only shows up when you
do a power down and then power up.
On a Thinkpad the changes you might make in the BIOS setup on other
machines are normally done with the Thinkpad Utilities which are
preinstalled on the machine. For some of the more obscure settings, you
may have to use the DOS command line Thinkpad Utility program, ps2.exe.
If you don't have the Thinkpad Utilities for your machine, you can
download them from
http://www.ibm.com/support/, select category
Notebooks, then go through the menus to find downloadable files for your
specific model number.