Hi, I'm David, and I'm happy to help you.
Follow the procedure below.
- Right-click on a file that is the extension you want to change and select "Properties";
- In "Open with", select "Change";
- In "How do you want to open <extension> file from now on?", scroll down and select "More apps";
- Then click "Look for another app on this PC";
- Browser to the location where the desired program is stored, select it, and click "Open";
After doing this, the desired program should already be selected as the default for the desired file type.
I hope this helps. Feel free to ask back any questions.