I really have no clue all tutorials I have watched iver don't work or just are not clear enough

Download the CS that you want and remember where you save it to. I save mine to C:\My Documents\My Downloads folder.

Go to that folder and find your CS. I unzip CS right to the same folder then open that folder. The folder you want will contain two OVL files plus one folder. The folder that holds the three parts is the one you want to move.

Now you have to go find the folder to put it in.

It will be something like this... C:\Program files\Roller Coaster Tycoon 3\Style\Themed

You will put your CS folder into the Themed folder. Only add one CS at a time. Do this while the game is closed. Once you add one CS, start the game and try using the CS that you just added. If it works, close the game and add another one then test it. If you add too many at once and one of them is not right it is harder to figure out which one is crashing the game.

When you test out the CS, if it crashes the game go look for that CS in the Themed folder. Make sure the CS folder is not inside of an extra folder. If it is it will show up as only having a folder within a folder without having the two files. If you see only a folder, drag that folder into the Themed folder and delete the empty folder.

You have to take care of any bad CS installations as they happen or using your CS will keep causing the game to crash and it will become a big mess.

Some CS downloads will contain a Readme file telling you where to put the folder.

CTR's and CFR's do not go into the Themed folder. Only CS goes in the Themed folder.

CS that uses Particle Effects is installed differently than normal CS. Ride Event CS is also different.