Connect to Network - Always On?

I just bought a brand new iMac and I have it connected to a PC network. It sees the network fine, but I was wondering if there is an option where I can always have the iMac automatically conenct to the network when the iMac is turned on.

I may be wrong, but when both computers are on at the same time and connected to the same router, then technically they are already connected to the network and ready to fileshare.

Both my computers are networked but I'm having a heck of a time with daily IP address changes.

I have learnt that this is normal behaviour but it's very annoying.

At this stage I haven't figured it out, but am working on it.