Kali 1.1 MITMf Not Working and a Question About Meterpreter

Hello guys, i just installed Kali 1.1 and i downloaded MITMf but it does not works.

And i can not ping this computer. But i know it works and it is not using HTTPS web sites. What should i do?

Also i have a question about Meterpreter, please help me.

Really, how it works? We are typing our local IP address, and if victim is not on our network, how it works?