The first thing to do is to make sure the software can find the mouse.
Work out which serial port your mouse is connected to - usually this
will be /dev/ttyS0 (COM1 under DOS) or /dev/ttyS1
(COM2). (ttyS0 is usually the 9 pin socket, ttyS1 the
25 pin socket, but of course there is no hard and fast rule about these
things.) There are also an equivalent number of /dev/cua devices,
which are almost the same as the ttyS ones, but their use is
now discouraged. For convenience make a
new link /dev/mouse pointing at this port. For instance,
for ttyS0:
ln -s /dev/ttyS0 /dev/mouse