How do I make DIY air freshener refills?

PA, here's a link with full instructions.

https://www.mom4real.com/diy-air-freshener-plug-refill/

Yes

Sorry if the link doesn't open for you correctly. I just tried it and it shows instructions with clear pictures, etc. Basically what it says to do is to remove the wick using needle nose pliers, fill about half full with an essential oil of your choice and fill to nearly the top with water, place your finger over the top and shake to mix the liquids together well, then replace the wick and screw the container back into the plug in and use as a new air freshener. Perhaps you have something blocked on your computer than won't allow the link to work as it does on mine.