hi guys how can i add squid service on my plesk control panel

my version is plesk7.5 linux version it runs on Fedora Core2

hope you can guide me thanks a zillion!

You have to install it from the command line. There are numerous how-tos on the net. There is nothing special about plesk that should interfere.

I am not sure what you are going to use squid for, but make sure it is not an open proxy. Scanners will find it and then you will suddenly have tons of traffic running through your server.