Sidebars allow you to add and display widgets inside your theme. Moreover, you can use sidebars to display widgets anywhere you want. So, if you want to add widgets in sidebars, consider this article.
It is very easy to add widgets in sidebars in WordPress, Consider below steps, to add widgets.
Step 1: Go to the admin panel > Appearance > Widgets.
Step 2: simply drag and drop or select widget in particular sidebar and save widgets.
For more understanding, see below image for more information.