I take it that squid is not
starting when the machine boots currently?
You need to know what your default runlevel is, you can find this out by typing:
from the command prompt, run man runlevel
for more details.
Assuming that your default runlevel is 3 and that you have a /etc/rc3.d folder.
ln -s /etc/rc.d/init.d/squid /etc/rc3.d/S99squid