Start by making sure you are in the Race or Die Home tab. Go to the orange Stats option at the bottom of the right hand column. Here is where you are going to see your overall Race or Die character statistics, how many experience points you have until the next level, the achievements you have made, the cars you have, the illegal mods you have, and other elements.
If you scroll to the very bottom of this Race or Die profile screen, you are going to see an obvious Reset button. If you press the Race or Die Reset button, it will give you a warning button and you continue by pressing OK. This will reset everything in your Race or Die account, except it will retain your crew size and you will keep the same Race or Die Friend Code.
The reason for this is that with the Race or Die Friend Code system the way it is, you would affect other Race or Die players if your reset dropped them from your crew. So instead, your Race or Die Friend Code remains active for any place you may have placed it and all your crew members stay where they are.