unclear how to reference a container image from an external registry

Description of problem:

Users are unsure what value to enter as the external registry value.

The placeholder says "Enter an Image name" however it's unclear of the format.

Image search is performed against docker hub however how does the user reference an image in quay?

Prerequisites (if any, like setup, operators/versions):

Steps to Reproduce

1. go to add page
2. select Container Image option

Actual results:

Expected results:

Placeholder text should provide a more useful value instead of simply telling the user to enter the image name. This text can include an example.

Or alternatively the helper text.

Reproducibility (Always/Intermittent/Only Once):

always

Build Details:

4.9.0-0.nightly-2021-06-20-015701

Additional info: