How to change default app to open certain file types.

It's not as simple as it seems :)
Although it's easy as pie to change default apps by type file, but how to do it if I want to use app that's not on the default Window list?
Like in this example,

File is opened by IE but I have installed in my system programme called Notepad++ and I want it to open .xml files whenever i double click on them. But Notepad++ is not on the Windows list

So how to set this up to open .xml files with Notepad++?

I've got it. Managed to resolved it by myself:) Thx for the tip though :)
For posterity, if they want to, that's what I did.
Went to MS store, I just thought that it's pointless as I already have this app installed, dl it but haven't installed. Since then, when I double clicked first .xml file, window popped up asking what app I want to use it to open this file and now, Notepad++ was on the list.
So now, whenever i double click any .xml file - it's being opened by Notepad++ as I wanted.