For details see [Theme section](https://www.keycloak.org/docs/latest/server_development/#_themes) of Keycloak developer docs.
As specified in [Deploying Themes](https://www.keycloak.org/docs/latest/server_development/#deploying-themes) section of the documentation, *themes can be deployed to Keycloak by copying the theme directory to themes or it can be deployed as an archive.*
During the development phase, themes caching in Keycloak configuration file has to be disabled. To do this edit `standalone.xml`. For `theme` set `staticMaxAge` to `-1` and both `cacheTemplates` and `cacheThemes` to `false`.