In short you don't.
All assets are to be uploaded to stage then deployed to production, this is a bit of a pain especially if your using custom content via admin and want to refresh images/message in admin without a push.
create a hidden/private board which only you have access too, then just upload your assets in new topics, you can then embed them wherever you want in community and because images are treated as a seperate object to posts they don't take the "private" permissions so anyone can view them if embedded on a public page.
Just some background on why assets go the publish route via stage: Since the asset manager is tied into the skin management and allows to overwrite existing live assets there is an added protective layer to prevent you from accidentially breaking your live community UI. The ide is that you upload first on stage, verify there, the push to production and review again in preview. Only then it should go live to production.
If it's really just about image upload I would recommend to use the user photo albums. You can reach them via the "My Photos" link on your profile page (if your community doesn't have that widget featured the URL is /t5/media/gallerypage/user-id/<userid>/tab/all). You can upload the pictures there and then conveniently insert them into your blogs or replies using the "Photos" button in the rich text editor:
Bonus tip for @Fellsteruk:
From your hidden board's options menu select "Subscribe". Then you will be able to quickly find it again at your Subscriptions list at /t5/user/myprofilepage/tab/user-subscriptions 😉
I did some further testing around this scenario and the results support and extend my recommendation:
For image resources that you want to upload, but not have exposed to the community right away you should follow these steps:
@ClaudiusH Here is another one for you. I went under studio " digital assets" and see some images from the community that I would like to download on my laptop so I can be consistent and use these images on community marketing material. Where are these files actually stored so I have access to do so? Thank You!
I assume you are referring to images your community team had uploaded to Studio -> Community Style -> Asset Library (from the dropdown selection) -> Other Assets.
You can download the original image asset from the file name link on the very left within the asset list. Easiest is to right click and select "Save as".
Bonus tip: If you are using Chrome browser you would love the Lithium Studio Bulk Uploader extension by Hinterlands. It will add image previews and a more convenient upload experience.