uri formats are not supported

I want to import an excel file regrouping several products in this category manage product. Under the category picture 1, I want to insert an external link leading to a picture. Jpg, but the following message appears "uri formats are not supported" Can you help me?

Without custom changes, you can't use image URLs.  You must use a local file path/name. (and if hosted, you need to ftp files to your host)