I install the ettercap-gtk and got it to work with ettercap -G (thanks again benx009)
And I have no idea how to use it...
I tryed the help on ettercap but I didnt realy understand much of it...
I have tryed looking for tutorials on the internet and again, didnt realy understand much of it...

1.Does anyone know of anything to help someone who is pretty much completely new to this?
2.What do I need to put as the ettercap input... I tryed "eth1" but this did not work?
3.What does the pcap filter do?

what are you using ettercap for if you don't really undersatnd what it does? what has lead you to try to use it in the first place? if you don't have a basic to moderate understanding of tcp/ip you're unlikely to ever really get much out of a packet sniffer like ettercap. the input will just be a suitable network interface, e.g. eth0. do you even have and eth1? pcap is the gneric library that 99% of packet anaylsis tools use to actually get their data. using a filter, like "host 1.2.3.4 or port 80" refines what data is captured in the first instance, rather than having to wade through irrelevant data within the app.

From the homepage of ettercap:
Do you know what is a LAN? And what is a man in the middle attack? What is a switch? etc...

What didn't you understand in the documentation?

Ettercap is very (too?) easy to use if you have a bit of background.