For the current version of Banished, you need Megamod 8.01, and it is not on Steam, but you can find it here: https://www.blackliquidsoftware.com/forum/Thread-MegaMod-8-01
You'll find that it's a .rar archive that contains MegaMod in 3 parts (which is why it isn't in the workshop).
Those 3 files need to be dropped in your Steam/SteamApps/common/Banished/Windata folder. In-game, you'll have to make sure they are in the right order (1 on top, 3 at the bottom) and enable all 3, confirm the changes to the mods menu, then entirely exit Banished and restart before starting a new town.*
Note that as it's a huge mod, depending on your computer and the DirectX version you use, Loading the game wiht MM enabled can take a very long time, during which you'll have a black screen. You can alt-tab to do other stuff or make a coffee while it loads. DirectX11 loads faster, but DirectX9 can avoid crashes for some people.


* That extra "exit Banished entirely and restart" is a step that should be taken whenever you make any change to your modlist. It avoids crashing when you try to quit your town to go back to the main menu or close the game. It's not an issue with the mods, but with the way the game registers mods. Nothing modders can do about it.