How can I can edit or change the following layer name? 
I am a self learner of PCB editor. I was trying to design the copy of a file I already have (A reference board file). The below picture is the top layer name of the PCB reference board file. The default layer name for the board I have been working on is simply "TOP". How can I change the class name from "TOP" to "L01_TOP". I know the layer name does not matter much, but I would like to know how to edit it.