In some cases, you may have an image, but do not know where it came from or if it is in the public domain or has a Creative Commons License.
Google Reverse Image search may help you find the source of the image.
Go to Google image search, and then select the camera icon in the search bar. This will allow you to either upload your photo or paste an image URL.
After uploading a photo, Google will attempt to find similar and exact matches. The exact matches will help you locate the original source.
In this case, this image is from an article in the BMJ Emergency Medicine Journal. A closer look at the article indicates that this image is under copyright, and cannot be used directly in the MedEdPortal submission.
Instead, you can search for similar images that are in the public domain or use Creative Commons.