Video Guide with Lethal Company as example

Text & Image Guide

A lot of mods follow a similar pattern, so I've created some generic examples for demonstration.
The locations where modded files go may vary depending on the game, engine, and modding scene.

Go to the pages for the required mods, such as for YeenBFishin, then click on the 'Manual Download' button to acquire the zip files.

Next open up the games base folder where the .exe is located and open up the zip for the modloader.

Often the modloaders downloaded from Thunderstore will have a root folder in the zip you want to open first.
The files in there are the ones you want.

After that select the ModLoader folder and related files
and drag them over into the base folder for the game itself

Likewise for the other mods you get, many will match the folder structure of the main modloader, and you can drag and drop that into the base folder as well and their contents should go right where they belong.
Others might not have any folders at all and will only contain the mod file. Those can usually be dragged & dropped into the mod folder as well.

Video Example