How to upload on Commons?
Here is it explained step by step:
- First register on Commons or log in (you might have been registered automatically via unified login already).
- Specify your interface language in your preferences for convenience.
- Go to Commons:Upload and follow the instructions. Experienced users can also use this tool.
- You can use all files from Commons here in the normal way under the same name.
Why is it disabled here?
Because of bug 11168! ;-)
There are several advantages:
- You can use your image on every wiki of the Wikimedia Foundation.
- It avoids having to re-upload missing files after importing all test wiki pages to the new site.
- Commons is specifically for files. Consequently it has a better policy, etc. Incubator doesn't have any control on uploaded images.