Hello Maureen2,
Tracking expenses for car trips is called mileage. In QuickBooks Online, there are 4 steps to follow to record this type of transaction. First is to set up a supplier. Secondly, set up an expense account for mileage. Then, set up a product/service item. Lastly, enter bills for it.
To see the full steps, please see this article: How to Track Mileage.
Let us know if you have any questions. Thanks!