1995 Escort GT issues

First, let me say I don't know much about cars. Second, let me ask for your help. The problem is odd. I replaced the thermostat and fan switch on my car. As far as I know, I put all the wires and such back correctly. When I start my car, it stays running for a few seconds. Then, it dies. I can keep it running a little longer if I press down on the gas pedal a little. But it still dies. After I replaced the thermostat and fan switch I removed the cap off the radiator and started the car to let it idle as the box said to do. Not sure if the radiator cap and the "pressure cap" are one and the same. If anyone can help me solve my issues, I'd surely appreciate it.