Can someone explain what the sentence that i highlighted with blue means.

Hello!

The specific sentence has "they" as the subject. I'm taking this as they = outsiders, so you could restate it as: The outsiders need to overcome the temptations to try and fit in by climbing into one.

Climbing into one is climbing into a box, as addressed earlier as well. This also means climbing into what is normal, what the trend is (As referenced by the phrase think out of the box).

Therefore, put the sentence this way: Outsiders need to overcome the temptation to try and fit in by following what is normal.

Essentially - people who don't fit in need to resist trying to fit in with others and not follow what is normal.

Hope this helps!

it is the : d because is true