The phrase "to fit into" means to be able to accommodate, adjust or adapt to a particular situation, condition or environment. It implies that something is being made to match or conform to specific requirements in order for it to work effectively or be accepted. For example, if you say "this shirt doesn't fit me," it means the shirt does not conform to your body size and shape, so it cannot be worn comfortably. In a broader sense, the phrase can also refer to fitting into social norms, expectations or group dynamics - meaning that an individual is able to behave in a way that is acceptable by others within their community or society.