The topics widget is a group of call-to-action banners that lead to your post categories. On the Cottonwood theme demo, it’s located under the homepage slider.
Go to Appearance >> Widgets.
Drag the Topics widget to the widget area where you want the call-to-action banners to appear. It is placed under the Home : Header widget area.
Add checkmarks to the categories which banners you want to show.
Next, go to Posts >> Categories.
Put your mouse over the name of the post category which banner you want to show, and click Edit.
Scroll down to the section where it says “Category Thumbnail”.
Click the “Add Image” button to upload the banner or image that represents that category.