How to update all existing assets with a new locale

There is a site which was already built without any dimension set/locale and it is live right now.

But, client wants to localize the site to different languages now. We want to go with single contribution site to have master-child relationship between translated assets. If that's case, I need to create the dimension set with different locales and need to update all existing assets with the global locale first. Is there an easy way to achieve this? Also, how should I make these changes in the prod live environment ( I don't want to publish all assets again).