I2C Lynx comunication between two Arduinos

[pbellido]

I am trying to comunicate two arduinos One (one as Slave and the other as a Master) using lynx libraries. I am not sure how to define one of them the role of master and viceversa. Both arduinos are conected to the pc using com Port 3 and com Port 4, and connected one to one using the SCL and SDA cables. 

I am not able to define an I2c slave adress and i cannot comunicate both. I think that I am missing something really important. It is my first time with i2c comunication.

[aol1aim1]

I have also been trying to do something similar to this with very limited success.