How to install a mod on steam

[Dkpj]

Hi,
I'm a new user of Steam (but not a new Rimworld's gamer  .
Maybe my question is very stupid, and sorry for that but I don't understand how I can install a mod from another seed of Steam.
Orion, a mod maker, has posted a link with a nice mini-mod, and I downloaded it.
Now, I'm alone with my mod cause I don't have anymore a file "Mods" like before (with my cracked version).
And Steam is totally obscure for me. To install my mods, I just had clik on " Subscribe" and it seems to work.
My difficulty is for this mini-mod. Can someone help me please ?
Thank you so much in advance and sorry for my bad english, I'm french.

[LWM]

Steam automatically downloads the mods; they appear under "Mods" in the main menu.  You turn them on from there.

[Haplo]

If you want to install a non-Steam mod in your Steam installation, you still can use the 'Non-Steam' way:
Find your RimWorld folder: ..\Steam\steamapps\common\RimWorld
Now go into the Sub-Folder Mods: ..\RimWorld\Mods  <-- If it doesn't exist there, just create it.. But it should normally be here.
Copy your Non-Steam-Mod into this folder. Make sure that it is extracted and you find the About.xml file there:
..\RimWorld\Mods\<NonSteamModName>\About\About.xml

Hope that helps?