Every widget has a settings panel where you can customize how it looks. Some widgets also have extra settings specific to what they do.

These settings are available for every widget:
Type a custom title for the widget. Click the clear button next to the input to remove it.
Pick an icon from the built-in icon library, or use a custom image URL. The icon or image appears next to the widget title.
Toggle whether the widget title is visible. Turned on by default.
Toggle whether the widget icon is visible. Turned off by default.
Choose how the widget card looks:
Pick a color for the widget card. Choose from the same 10 colors available in Appearance settings: Default, Red, Pink, Purple, Blue, Cyan, Lime, Green, Yellow, and Orange.
Many widgets have additional settings below the common ones - for example, a Weather widget lets you choose temperature units, and a Links widget lets you control how links open. These are covered in each widget's own documentation page in the Widgets section.