On the edit properties page of the equipment you would like to edit, select the docs tab. Drag the image you would like to use anywhere on the browser page.

Let the image upload. It will then show up on the documents list and its ID will be blue (only happens for image files. Other files will not show a blue link as the ID.

Click the ID number. The equip image on the top left will change to show the image you just uploaded. A green marker will be displayed on the docs list to show which image is currently selected as the equipment image.

You may delete the image from the docs list. This will not delete the equipment image.