Can someone help me install the toybox mod. Explain it to me like I'm five

I really feel like an idiot. I've installed mods on other games, and every time it's a struggle. I try looking online for instructions, but I don't know what I'm doing. I want someone to explain step by step how I install the toybox mod for rouge trader. I've downloaded the file, but i don't know how to install it. i am playing the game on steam with a Microsoft os

I just want to be able to change my origin backstory, so i don't get echo of torment.