To begin the install, first go to the downloads page (http://www.mods-for-grx.com/downloads.html) and press the download button next to PSTC for GRL3 + GR2A. Then download should initiate automatically.
Figure 1 - Mods for GRX downloads page
After the zip folder is downloaded, double click the folder to open it. Then click "Extract all" from the windows explorer toolbar.
Figure 2 - Compressed CTC install folder
Once you have the folder extracted, click only the setup.exe file. Next, click run or install on any security warnings that may pop-up.
Figure 3 - Extracted CTC install folder
Finally, once complete CTC should initiate automatically and you can enter your product validation information.