how do I enable mods for online

[van]

I wanna use mods from the workshop but it says local mods not allowed

[Monch]

When setting up a multiplayer world, you can only use mods that have a steam icon next to them. Those mods are public, and can be downloaded by anyone. If the mod has a folder icon next to it, it means that you installed the mod manually, and the game doesn't know where to tell other people to download it from.

[OncaLupe]

You'd need to publish the mod to the workshop so that it can be downloaded by players.

[RhoDawg]

Also, if you are connecting to a dedicated server, they need to be enabled on the SERVER, not at the client for it to work.
The patch video shows how to add them through the Dedicated server console.