The Walking Dead: The Final Season

First, you need to do this:

The first is a Boar Skull found in the greenhouse courtyard before you go inside.
The second is a mushroom in the first room of the greenhouse. (Eat a second one for the Edible achievement.)
The third is a Venus Flytrap in the second room of the greenhouse.

Place them when you go back to your room with AJ. (I did that before looking at the shirts, just in case.)

Here's a video guide that I made covering all the collectibles for this episode. I've also made some notes below describing where they are.

The Walking Dead: The Final Season Episode 2 Collectibles Guide

There are three collectibles in Episode Two and they can be found in the Greenhouse/Lab areas which is towards the end of Act 2....

Boar Skull - Found directly behind you before going inside the Greenhouse.

Mushroom - Can be found inside the Greenhouse on the flowerbed that's directly in front of the cabinet where you get the Barbed Wire from.

Venus Flytrap - Can be found inside the Lab, it is directly in front of you
on the flowerbed on your left.

Once you have all three collectibles you can place them in the following locations in your sleeping quarters.

Boar Skull – Can be placed on the shelf on the right side of the room.
Mushroom – Can be placed directly underneath the Boar Skull.
Venus Flytrap – Can be placed on the bed side cabinet next to the bunk beds.

Hope this helped.