How do I swatch image instead of color

Step: 1

In your shopify Admin panel, under THEMES & SETTINGS section in the left sidebar menu, click on the "Swatches"

Like this:

Step: 2

Now you can see "Option Display" section.

Like this: 

In this option fields, you can see the "Image". Just select this.

After selecting all, the output will be...

Step: 3

In the "Swatch Value" field, add the images url.

After adding images url, the output will be looks like this:

Step: 4

Once you done with all the settings. Click "Save" button.