IIRC, OS3.1 runs fine with KS3.0. OSes 3.5 and 3.9 must have KS3.1.
There are 2 roms and 2 sockets, you must match each rom to the correct socket (there should be instructions). You must also match the ends with the notches to the silkscreen notches.
Finally, the rom chips are in the form of dual in-line packages (dip). Often, when new, the 2 rows of pins are not parallel to each other. Instead, they are splayed, when viewed from an end. If they are pushed into a socket this way, sometimes 1 or more pins will bend. To prevent this, first lay the chip on each side on a flat surface and gently bend the whole row perpendicular to the chip body. If all the pins are pointed straight down, they won't bend when pushed into the socket.
Oops, while typing this long answer, someone answered you already. This is probably well known, anyway.
