Usage patterns
〈事〉には慣れが必要だgetting used to ~ takes practice
It takes some practice to get used to a new job.
慣れの問題だit's just a matter of getting used to it
It's just a matter of getting used to it, so you'll be able to do it soon.
慣れで〈動詞〉ようになるbecome able to do something through habituation
Through practice, I became able to operate it naturally.
慣れが出るfamiliarity leads to carelessness
Getting too used to it made me forget an important check.
〈物〉に慣れがあるto be familiar/comfortable with something
He's familiar and comfortable with this machine.
Expressions
慣れっこになるget used to; become accustomed to; become familiar with 習うより慣れろpractice makes perfect; experience is the best teacher; you learn best by doing