To add the route, use the following syntax,

/usr/sbin/route add host [destination ip] [via ip]

Then add this as well to your routes script (so it survives a reboot) in the /etc/rc?.d, i normally just do a find for the routes file in /etc.

find /etc -name *routes* 

 If there isnt one then you will need to create a route start up script within /etc/rc3.d.