This is not really the preferred way anymore but this will cover for the people who still download mods this way :)
Website - https://mods-unturned.com/

First find the mod you would like to install, download it
Navigate to your directory of your Unturned game
[Installing maps]
Get the downloaded map file and then extract it anywhere and then move the folder extracted inside the 'Maps' folder.
[Installing any other mods]
Get the downloaded map file and then extract it anywhere and then move the folder into the 'Bundles' folder, if it says replace then click yes but it normally wouldn't
Now hop into your singleplayer game and use the map or mod

Most mods will make you have to spawn the item from the mod for example a gun
To spawn items use the command give name/id/quantity
To give vehicles use the command Vehicle name/id

Thanks to 3.11 we can now use the Steam's integrated workshop to handle our mods.
Some mods will automatically be able to install to your game but some may require you to install the contents of the mod manually
This part of the guide is only for those mods that need manual installation
First subscribe to the mod, this mod will now be located here
D:\SteamLibrary\SteamApps\workshop\content\304930
Inside this folder you will see all of the subscribed mods
Find the right folder for your selected mod and copy the folder
Navigate to your directory and place it in the 'Bundles' folder
D:\SteamLibrary\SteamApps\common\Unturned\Bundles
Place the mod folder in here

Thats the mod installed, now depending on the mod you will probably need to manually spawn the items into your world
To check if the mod is installed open up 'Unturned' and goto Workshop, edit, and then find the items on the relevent menu's

Hope this guide helped everyone :)
If any help is needed feel free to comment or message me.
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