How to Set Symbol Mapping?

Click on the Copy Setting button on the left-hand side of your Master or Slave account. A small window will pop up then click on the Symbol Settings button. Define the Master and Slave Symbol for each.

Important to remember that you have to enter the exact symbol (case sensitive) for the master and the slave in the mapping, and don't forget to click Add mapping button. 

Here's a video about Symbol Settings and Symbol Mapping: