HIMEM.SYS File missing?

I am running on Win98 and when I boot the computer it boots and the video is there for the initial pages of the boot process but then no icons or menu bars are present after it is done, the screen is completely white.  I tried to run scandisk from dos and it came back with no extended memory driver loaded on computer and that I needed to add DEVICE=C:\WINDOWS\HIMEM.SYS in the Config.sys file.  I do not know how to do this.