There are 3 placefiles that must be loaded into GRX in order for Radar Toolbox to work. To load them, press Placefiles to Add on the main menu of Radar Toolbox. Click the placefile you wish to load in order to copy the file path to your clipboard.
Figure 1: Radar Toolbox for GRX Main Menu - Placefiles to Add
Next open the GRX placefile manager (Windows>Show Placefile Manager) and press the + to add the file. Paste the file path into the textbox using Ctrl+V or Right Click and Paste. Once you have the file path pasted, press ok.
Figure 2: GRX Placefile Manager - Adding a placefile