has ... of/about itThis is not a fixed expression by itself. It combines the reflexive pronoun s', en, and est, and its meaning depends on the verb that follows. For example, s'en est sorti means “got out of it” or “got through it,” while s'en est plaint means “complained about it.”
FR: Elle s'en est bien sortie malgré les difficultés.
EN: She got through it well despite the difficulties.