In this theme, we paid special attention to Sidebars for your biggest convenience and on multiple previous requests. We have two types of the sidebar: Now how it works.
1) Sidebars - Custom Post type which you build by means of Visual Composer and can insert into a page via the STM Sidebar Visual Composer Module.
2) Appearance - > Widgets - > Sidebars which you build by means of regular WordPress widgets and insert into a page by means of Widgetized Sidebar Visual Composer Module. So, in our posts, for example, we use Widgetized Sidebar - > Right Sidebar.
If you want to insert Custom Sidebar, you should use STM Sidebar Module - > Choose one of the pre-created ones.