meaning of fit in

1- fit in: to belong to a group, plan, or situation
example:    He didn't fit in with her plans, so she left him.

2- fit in: to be accepted by a group of people because you are.
example: She fitted in with her new colleagues straight away.

3-fit in: to have enough time to deal with someone or something
example: Dr Halden can fit you in this morning at 10.