Update README.md

Author: f-riente

README.md

@@ -20,7 +20,7 @@ The code is structured in different folders:
 - simulation
 - performance_analysis
 
-Within the _GUI_ folder, you can find the file `mainWindow.mlapp`. Run this script to launch the mainwindow of the tool, where you can select the outputs to be printed, select the circuit to study, set the input stimuly and choose between the YIG100 and YIG30 technology node.
+Within the _GUI_ folder, you can find the file `mainWindow.mlapp`. Run this script to launch the mainwindow of the tool, where you can select the outputs to be printed, select the circuit to study, set the input stimuly and choose between the YIG100 and YIG30 technology node. **Before starting the simulation from the GUI, please move to the root folder of the repository.**
 
 The _simulation_ folder contains the core of the computational model for the two technology nodes. In addition, it is possible to find also the description of the supported circuits.