1
general::
One needs to become accustomed to something. For example, We've always had a small car, so driving a big van like this? well, it takes getting used to. This idiom employs used to in the sense of "accustomed to," a usage dating from the first half of the 1500s.
American Heritage Idioms
2
general::
Phrase(s): It takes (some) getting used to.
It is very unpleasant at first, but after a time it will not be so bothersome. (Said in recognition of the unpleasantness of something.) • I never ate raw oysters before. It takes some getting used to. • These hot Mexican dishes seem impossible at first. They take some getting used to, I agree. But it’s worth it.
McGrawhill's American Idioms And Phrasal Verbs