Get image from Adobe Stock and download to your computer.

Go to: https://www.canva.com/  

Click on Create a design and + Custom Size.

Enter 800 x 500 px (OR Select 800 x 500 by clicking on it).

Drag and drop image into custom size field.

Position Image in upper left corner of field. Drag lower right positioning dot down and right so image fills the space.

Adjust image within the field. Whatever is outside of the field will be cropped off.

Click on Untitled Design area and type in the new name.

Click Download.

See downloaded cropped image in lower left.

Click on Go to your homepage.

Your design will appear under Your Designs.

Click on 3 dots and select Move to Folder.

Select your folder. (You may need to create a folder first.)

Click Move here.

Now your correctly sized cropped image is downloaded to your computer and ready to add as a Featured Image to a Testimonial post.