Ok so first off your going to need something to edit the picture templates with. To do that you can use Paint.net which is free.
http://www.getpaint.net/index.html (Make sure you read the requirements if you can't get this to work)
I'll do this step by step.
1. After you install paint.net you will need to download one of the template files. In this case because we are using Paint.net to create the car mural we download the .pdn file which for the car we are working on is
2. Open the file with Paint.net. You will notice that there are 2 layers:
Ok so Main is your main section that you will be working on. The outline is just there to help you see where on the car the car patterns or car mural will end up.
4. So I'm going to create something basic so you get an idea. What you will want to do is make sure Main is selected in the Layers screen, but leave both Main and Outline checked. I'm going to be using the line tool on the Tools bar and setting the color to navy blue.
NOTE: With the new template system MAIN has been renamed to USE THIS
5. Ok so I am going to draw a line on the side of the car.
From there you can create lowrider patterns however you want. Make sure you save it somewhere so that you can work on it again later. Go to the next step if you want to learn how to add murals or skip that and go to step 11.
7. Now to add a mural you will need to get the picture you want to add and open it with Paint.net. There are different types of pictures also. So for example I'm going to use a transparrent image. If you where to use a non transparrent image you would see the background of the image on the car(white/black). Once you get confortable with paint.net you can edit pictures that arent transparrent and turn them transparrent. I'm going to use a transparrent png image as a mural on the trunk of my paint job.
8. So what you want to do is after you open the image in Paint.net that you want to use is go to Edit --> Select All then go to Edit --> Copy. That will place the image in your clipboard so you can add it your paint job. So now if you didn't close your template we worked on before it should be on the top right under the X to close the window. Click on it to bring it back up. If you do not have it there then open it back up from the location you saved it in earlier.
9. Ok now that you are back at the original template picture you can go to Edit --> Paste. This will paste the image you wanted as a mural. From there you can drag it to the location you want and resize it or rotate it. To move it just click and drag it around. If you wanted to resize it there are little boxes on each corner of the image. You can click and hold one of those boxes to resize the image. If you hold SHIFT on the keyboard while moving the boxes it will keep the same aspec ratio.To rotate just right click and drag your mouse.
10. Now to save your mural. On the layers box that I had you select Main before you will need to uncheck the Outline check box. You will notice that the outline will disappear. Now go to File --> Save As --> Enter a name and select PNG as the save as type.
11. Now that you have the image on your hard drive you can upload it somewhere and use it as a mural. I used ImagShack.us to upload my image. After you upload it you will want to view the image and get the image URL.
It is very important that you get the direct link to the image. if the link does not lead directly to the image this will not work. The image height and width have to also match.
12. Now go to you mycars page and enter the image link as your mural and your done. Next time you play the game or someone plays against your car the image will be displayed.
Here is a screenshot that shows an example of what you can do: