How do I put cushions on a hard wood headboard?

This tutorial might help. Good luck! https://www.craftberrybush.com/2013/11/our-new-old-headboard-how-to-upholster-an-old-headboard.html

here's bunch of videos to upholster it take your pick https://www.youtube.com/results?search_query=diy+upholster+head+board

You can upholster the headboard like other Hometalkers did.

https://www.hometalk.com/search/posts?filter=upholster%20headboard

I agree with the other comments! Your best bet would be to upholster it. If you want to keep the look of your wooden headboard, you could also get two tv pillows.

https://amzn.to/2EyAv4r

It is not difficult to cover hard wood with a cushion pad you can buy for patio furniture, mattresses etc. Use a thicker foam pad like 3 or 4 inches thick for the most comfort and attach it to the wood with appropriate glue. Then cut a cloth to cover it and staple it to the back of the board. That way you do not have any sewing to do.

You can wrap the headboard in fabric for support. You would add foam and batting to the front of the headboard, then stretch fabric over it all and staple fabric to the back of the headboard.

I would think some sort of velcro would hold cushions in place and you could still remove them to wash them if needed. Another idea would be those pillows that sort of stand up pillows used for watching tv (I know amazon has a lot to choose from).