You might be required to provide your mobile application’s URL in various signup pages, such as Amazon Associates affiliate program. The input text field might say “Enter Your Mobile App URL(s)” and it might provide a sample URL format as a hint text, such as “amazon.com/dp/B00AQL8VU4”
If you have a mobile app, you can type its URL in the format you see in the help text in the input textbox, that is: amazon.com/dp/ASIN, where ASIN is the unique ID for your app in Amazon Appstore. The easiest way to find it, is to browse the web version of the Appstore, find your app, and then look into its URL in the address bar, where you will see something like this (ASIN is underlined):
Or scroll further down on your products page, and your app's ASIN will be the first item in the 'Product Details' section:
Copy your ASIN, paste it after the amazon.com/dp/ part in the textbox, and hopefully you should be able to proceed to the next step with your registration.
Keywords: mobile app URL, application ASIN