From what I understand, you would append it after the kernel name in your loadlin line.

For instance if your kernel was vmlinuz stored on C: then

loadlin c:\vmlinuz root=/dev/hda3 ro mem=###

The syntax for loadlin is

loadlin [kernelimage] [options] [parameters]

See: http://www.linuxdoc.org/HOWTO/Config-HOWTO.html