Prepare Your Addon:

Ensure your addon folder is complete with all necessary files (models, materials, Lua scripts, etc.).

Create a Workshop Item:

Launch Garry's Mod and go to the main menu.

Click on "Addons" and then "Workshop".

Click on "Publish" to open the Workshop Publisher.

Fill in the Details:

Select your addon folder.

Fill in the title, description, and tags for your addon.

Add a preview image to make your addon more appealing.

Upload Your Addon:

Click on "Publish" to upload your addon to the Steam Workshop.

Wait for the upload to complete. This may take some time depending on the size of your addon.

Share Your Addon:

Once uploaded, your addon will be available on the Steam Workshop.

Share the link to your Workshop item with others so they can download and use your 2D NPC.