Have you tested that the mod works as an add-on, and that when you start a new game your creation changes are present?
After that, for the workshop:
As long as everything you are editing is contained within your mod folders you can upload pretty easily.
Go to Project > Project settings. Fill out all your info, add a thumbnail image.
Save
Then go to Project > Publish Project
Make sure Steam Workshop is selected. Then off you go.
