I have an ArcGIS online app you can see here: http://arcg.is/2mqx9Ez. I just want this to work with the GPS on a persons phone so that the map will center on the user's location. How do I do this? Do I use javascript.

[ChuckThomas1]

This is an app for walking the Tejano Walking Trail which can be accessed here: http://arcg.is/2mqx9Ez  I want this to work with a phone so that it centers on a person's location if their GPS is on. How do I do this? Do I need to edit the app with javascript?