12 LED resistance circuit help

Hi, I want to make a simple LED circuit with 12 LEDs running off a
nine volt battery. I've managed to dig up enough information about
most things, so I know I'll have to wire them in parallel. But the
resistance I should be using still confuses me.
Should I have one (or more) resistors at the beginning of the circuit?
Or one before each LED in the circuit?

The LEDs I'm using have a 3.6v voltage drop, and they are supposed to
get 20mA I beleive.
So that's 12 LEDs off a 9v battery.

I have a bunch of 27 Ohm resistors because that's what I (probably
mistakenly) calculated I should have before each LED. But I have no
idea what i'm doing. So if anyone can help me out on what resistors I
should use and where I should put them that would be greatly
appreciated!

Thanks,
Steve
.

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