Instructions
Download a modding patch at gtagaming.com. Click on "Download" and follow the on-screen instructions to complete the download process.
Install the modding patch that you downloaded. Click on the patch and follow the on-screen instructions given.
Visit gtavision.com and download SparkIV. Click on "Download Now" and follow the download instructions.
Open up SparkIV and click "Open."
Choose a car mod that you would like to add to GTA IV and click "Import."
Click "Rebuild" and "Save."