You can add and configure sidebars here. But, to add tools to the sidebar you should go to Appearance>Widgets.

Add a Sidebar

• Go to Appearance> Customize> Sidebar Settings
• Click Add New sidebar
• Give the sidebar a name
• Click on Publish

You can see the new sidebar in Appearance> Widgets. Add a widget to the sidebar and click save to configure the newly created sidebar.

Configure Sidebar

• Login to your WordPress Dashboard.
• Go to Appearance> Customize> Sidebar Settings
• Select Sidebars for various Pages, like Blog Page, Single Page, Single Post Page, etc. The sidebar selected under the particular pages will only be displayed on the page. For example: Blog Page Sidebar appears only on the blog page.
• Click on Publish