In 1984 (part 3 - chapters 4-6), how must Winston change his feelings toward Big Brother before he can be released?

Winston tells O'Brien in the end of chapter four that he
hates Big Brother. O'Brien responds with the truth that Winston must face in order to be
released. That hate must transform into love. The love
cannot be a fake love. Winston cannot just say that he loves Big Brother because his
lies can be detected. Thus, this love must be real and meaningful. This authentic and
genuine love needs to not be coerced, although efforts in room 101 will help that
occur.

This becomes a central theme in the last several
chapters as the book closes with Winston finally allowing himself to love Big Brother.
In fact, the final words of the book demonstrate that this change is absolute and
complete when Orwell ends with the four
words:

He loved Big
Brother.