Foursquare app url help

when using foursquare, and creating a new app what do I put in the application url space?

for context I’m working in the codeacademy page on the wanderlust project.

https://www.codecademy.com/paths/web-development/tracks/webdev-intermediate-javascript/modules/intermediate-javascript-requests/projects/wanderlust

I used the following, and had no issues:
https://www.codecademy.com/courses/introduction-to-javascript/projects/wanderlust

Good luck!