Type in 'Default Apps' and select it form the search results. This will open the settings app
Here you will be presented with standard application types (ex. Mail, Photo Viewer, Video Player, Web Browser)
Navigate down to Web Browser and click the icon for the currently selected browser. This will present a list of available options that can be set to default. (For Dartmouth provisioned Windows 10 computers you should see Edge, Chrome, Firefox and IE 11 (now deprecated) as options.
Select the application you would like to make default and you should be all set! You can close the Settings app and the next time you click a web link from another app, it will open in your new default web browser.