Add Small Image Size to Media Settings

You can register a new image size by using add_image_size()

add_image_size( string $name, int $width, int $height, bool|array $crop = false )

Parameters

$name

(string) (Required) Image size identifier.

$width

(int) (Required) Image width in pixels. $height (int) (Required) Image
height in pixels.

$crop

(bool|array) (Optional) Whether to crop images
to specified width and height or resize. An array can specify
positioning of the crop area. Default value: false