You can customize general permalink settings from the
Settings > Permalinks page. That page has general WordPress permalink settings.
Customize the permalink settings of post type and taxonomies
If you want to change post type / taxonomy permalinks, you should use a plugin. If you change permalinks of post type from the codes of the theme, you can break the theme. The best way to change the permalinks are using a plugin. We recommend Permalink Manager Pro for this process. Also you can review or try free version of the plugin, click for lite (Free) version.