This article speculates that you've already correctly installed ROMRaider onto your PC.
- Download and save your .xml to a KNOWN location on your PC.
- Open ROMRaider
- Navigate to the 'ECU Definitions' menu option
- Select 'ECU Definitions Manager'
- Click the 'Add...' button
- Select the .xml you would like to load from your KNOWN download location
- Click 'Open'
- Click the 'Apply' button
- Click the 'Save' button
Lastly, attempt to open you ROM. While doing so, I generally check the 'Ignition Timing B' table to ensure that it appears to load correctly.