The Steam Workshop makes it easy to discover or share new content for your game or software. Each game or software might support slightly different kinds of content in their Workshop, so it's best to check out the official documentation for more details on what can be created and shared in that area.
When you find content you wish to add to your game, click the 'subscribe' button. In most cases the content will be automatically available the next time you launch the game. But some products require that you go into a dedicated area of the game or software to activate or access the new content.
These are the Steam Workshop features utilized by Total War: ATTILA:
Items posted in this Workshop are ready for immediate use. Click the Subscribe button on the detail page for the item and it will be available when you start Total War: ATTILA.