Wireshark question from a Newbie

[Yoman]

Hello!
I am pretty familiar with Linux, but now I'm using BT for the first time.

I am installing it because a lot of reasons, but one of them is this: I want to learn how to gather information from the internet (especially passwords). I am downloading BT ATM.

Meanwhile, I've installed Wireshark on my Mac. I am very new with it.
My question is: should I learn to deeply use it? And if I do, where should I look? User guide?

Sorry for the silly question and thanks in advance!

[sickness]

I want to learn how to gather information from the internet (especially passwords). I am downloading BT ATM.

I guess some things are really hard to understand.
We will not support nor tolerate illegal activities here.