Go to the Upgrade Screen with the car you wish to upgrade selected. Once here, select the component you wish to upgrade by using the tabs at the bottom of the screen. You can then scroll through different level upgrades on the screen by swiping left and right. Once you've found the upgrade you want to fit, either buy it, or tap "Re-fit Part" to fit it.
How do I add or remove upgrades?
Last Updated: 108d