Server Configuration help...

Okay, I'm having trouble trying to figure this out. This should be pretty simple but I just can't seem get my head wrapped around this.

I have a server, running windows server 2012 and 2 clients, running windows 7 professional.

For the clients, I have only one nic card that has the internal ip connected to th server through domain.

The server has 2 nic that's one connected to an internal network and one connected to the external network.

The problem I'm having though is that the clients doesn't have any Internet access but they're connected to the server via internal network, who's ip is different from the external (Internet) network.

Does anyone have any insight?