You can use high mileage oil in a new car without harming the new cars engine or low mileage engine.
However the new cars engine or low mileage engine will not really benefit much from the use of high mileage oil but it can help protect the seals and bearing from eventual wear when it does start to rack up high mileage.
Usually cars engines do not need high mileage oil until the engine reaches 75,000 miles or more and then the engine would benefit much more from the use of high mileage oil.
As an engine gets more mileage it naturally uses more oil due to worn piston rings, valves seals etc.
So by using high mileage oil your engine will last much longer than using conventional oil and you will not do any harm to your new engine and may actually help it last longer.
But for me I would just use conventional oil until it got to 75,000 miles or more which then the engine will benefit more from the more expensive high mileage oil.
Change your regular oil every 3,000 to 6,000 miles along with your oil filter and your engine should last a long time.
Then I would switch up to the high mileage oil when the engine gets to as much as 75,000 miles or more.