に慣れる expresses that something has become familiar and no longer feels strange or difficult because you have experienced it many times. The particle に marks the thing you are used to. For actions, use the dictionary form of the verb followed by の, turning the action into a noun phrase: 毎朝早く起きるのに慣れた means 'I got used to waking up early every morning'.

This pattern is common in everyday speech and writing. It describes a state that develops over time, not a sudden change. You can use it for both positive and negative situations, like getting used to spicy food or getting used to noise. Note that the subject is usually a person, but can be an animal too.

When you want to say 'I am not used to something yet', use the negative form: まだ慣れていない. This is a natural way to express that something is still new or difficult.