Dreamweaver 2021 how to create image border

Adobe has removed all image editing functions from the latest version of DW.

Here's the official announcement: https://community.adobe.com/t5/dreamweaver/image-optimization-workflows-deprecation-in-dreamweaver/td-p/11310914

Like Nancy states, use Photoshop for image editing, or CSS if you're just adding styles like borders, shadows, margins, etc.

To add CSS to your image, you can work manually in Code View, or you can try the new-ish CSS Designer under Window > CSS Designer.

AFAIK, Dreamweaver was never all that great for images as that's what Photoshop is for.   Assuming you're pressed for time and don't want to fire up Photoshop, you can use CSS properties to add borders, margins, and padding around your images.  Adjust CSS values as needed and add a border class to your images.

CSS (goes in your custom external stylesheet)

.border {
border: 12px solid #EAEAEA;
/**optional**/
border-radius: 10px;
margin: 1%;
padding: 1%;
}

HTML:

<img class="border" src="https://dummyimage.com/1200x400" alt="Placeholder image">

Related:

CSS Box Model - https://www.w3schools.com/css/css_boxmodel.asp