Creating a custom pet/pets?

Hey guys, I love the game but would really love for myself to have two pet cats ingame

I found a youtube video about it:

Creating custom pets:



I have done some modding with "stardew Valley" and Minecraft, and I love Terraria and would love to get my own custom pet.

I found a video where someone goes through the steps, I just don't understand how he got the scripts that are in the folder I have already drawn my own animations and have modloader.