Once you’ve made a map that you want to release, open the local map in Pogostuck and open the pause menu. Here you choose “Manage Steam Workshop”, then find an empty map slot and press “UPLOAD”!
If you want to update a map, you just do the same thing but choose the map slot that has the map you want to update.
Since Blender uses some absolute paths that are specific to your system, sharing a Map Project can be a little anoying. Here’s how you could do it:
Make a copy of your Blender file and open it. Go to File->ExternalResources->PackResources, this will pack all the external resources like images and models into this blender file. Then compress the project folder with the packed Blender file to a ZIP and then you should be able to share it with others.