How is Jane Eyre's arrival at Thornfield is an important milestone in her journey from innocence to experience?

Jane's arrival at Thornfield Hall marks the end of her
needing to rely on others for care and the beginning of her earning her own way. 
Initially, she must rely on the so-called "care" of her Aunt Reed and the abuse from Mr.
Brocklehurst at the orphanage.  After years of suffering, Jane strikes out on her own to
begin work as a governess and to fend for herself.  This leap into independence is one
way that Jane moves from innocence to experience.

Another
way that Jane makes this thematic move is her awareness of her feelings for Mr.
Rochester.  Despite his aloof manner, she is falling for him and becomes jealous of a
rival suitor.   She has, in a sense, been awakened as a passionate woman rather than a
girl.

Finally, Jane learns what it is to care for and even
forgive others.  She learns her Aunt Reed is ill and takes steps towards forgiving her
for her terrible abuse.   This action helps her ultimately forgive Mr.
Rochester.