In Windows 10, to change which app opens a certain file extension by default, please do the following:
Step-by-step guide
In file explorer, Navigate to one of the files that is of the type you would like to change
Right-click the file
Go to Properties (usually at the bottom of the drop-down menu
Click the Change... button
Select the new app you would like that file type to open with
Click the Apply button at the bottom, then click OK and that file type should now open in the selected application by default
DefaultThere is also a page under the Settings app, under Apps > Default apps