Name nodes on Simulink
To transmit the signal in this way, you have to use (From and Goto) blocks. 


However, in your example they are using voltage sensor along with (From and Goto) blocks. If you double click Vout, for example, you will see this,



Which is, from left to right, PMC port, Voltage sensor, PS-simulink converter and Goto blocks, respectively. Then we are using From block to receive Vout signal and plot it.