How to Add Widgets to the Sidebar of the Twenty Fifteen WordPress Theme
The left side of the Widgets page lists all the available widgets for your WordPress site. The right side of the page lists the widget areas designated in your theme. Drag your selected widget from the left side of the page into your chosen widget area on the right. For example, to add a search box to the sidebar of the default layout of the Twenty Fifteen theme, drag the Search widget from the Available Widgets section to the widget area.
To add a new widget to your sidebar or footer, follow these steps:
Choose Appearance → Widgets from the Dashboard.
The Widgets page appears.Editing the Recent Posts widget options.
Decide which widget you want to use from the Available Widgets section.
For the purpose of these steps, choose the Recent Posts widget.
Click the widget title and then drag and drop the widget into the widget area on the right side of the page.
Drag the Recent Posts widget to the widget area.
Configure options for the widget as desired and then click Save.
Each widget has different options that you can configure. Some widgets have a number of editable options; others simply let you write a title for the widget area. The Recent Posts widget has two options: one for editing the title of the widget and one to determine how many recent posts to display. Open the widget by clicking the arrow to the right of the widget title to explore the options available.
(Optional) Repeat steps 1 through 4 to add more widgets to your layout.
Arrange your widgets in the order you want them to appear on your site by clicking a widget and dragging it above or below another widget. Repeat this step until your widgets are arranged the way you want them.
After you select and configure all your widgets, visit your website in your web browser and you can see that your site’s sidebar matches the content (in the proper order) you’ve arranged in the widget area on the page on your Dashboard. How cool is that? You can go back to the Widgets page and rearrange, add, or remove items to your heart’s content.
To remove a widget from your sidebar or footer, open the widget title’s drop-down list and then click the Delete link. WordPress removes the widget from the widget area on the right side of this page and places it back in the Available Widgets section.
If you want to remove a widget but want WordPress to remember the settings that you configured for it, instead of clicking the Delete link, simply drag the widget into the Inactive Widgets section on the left side, near the bottom of the page. This stores the widget, with all its settings, for future use.
Another method of managing widgets for the Twenty Fifteen theme involves using the theme customizer to reorder, add, delete, and edit widgets: Click Appearance→ Customize → Widgets → Widget Area.