Which word for import? (들여오다 , 수입 , 가져)
I'm trying to ask is a car imported.

Is your car imported?
너의 차룰 들여왔어요?

I want to import a BMW.
나는 BMW를 들여오고 싶어요.

That car is an import.
그 차는 수입 이에요.

Am I using this word correctly?
Do I need to use 가져?

Question

Which word for import? (들여오다 , 수입 , 가져)
I'm trying to ask is a car imported.

Is your car imported?
너의 차룰 들여왔어요?

I want to import a BMW.
나는 BMW를 들여오고 싶어요.

That car is an import.
그 차는 수입 이에요.

Am I using this word correctly?
Do I need to use 가져?

Answer

Is your car imported?
너의 차룰 들여왔어요?  "너의" is impolite  and awkward here.  It sounds better without it.
=> 차를 수입했어요?  ("들여왔어요" is like "...brought the car in?", a little vague)
=> 차가 수입차예요? ("Is your car an import?" - this may be the best)

I want to import a BMW.
나는 BMW를 들여오고 싶어요.
=> 나는 BMW를 수입해 오고 싶어요.  
(Note that both sentences can be taken as  "I'd like to import BMW for business")

That car is an import.
그 차는 수입 이에요. 
=> 그 차는 수입차예요. (people usually say it this way)
=> 그 차는 외제차예요. ("That car is a foreign make" - another way people say it)

"가져" doesn't seem to fit in these sentences.