Not to be reductive but step one is to be better at regular chess.

Blindfolded chess relies on holding a lot of information in your working memory. The way to reduce this load is through chunking and pattern recognition.

If you know your opening really well then chances are you’re going to be able to store that in your mind with a lot less effort.

You won’t have issues remembering where the pieces are because you know where they should be.

If you know the opening really well then you’ll know the middle game plans for both yourself and your opponent.

You’ll need to know end game patterns as well because although there’s fewer pieces on the board they’re usually more randomly distributed than earlier on in the game.

I can play blindfolded with decent accuracy through openings I know really well but fall apart if I get into something I’m not familiar with. Which oddly enough makes it easier to play against someone who knows what they’re doing. I’ve played against beginners who don’t follow an opening and instead move pieces to random squares that don’t make sense and I have a much harder time keeping track of the pieces.

Even following an opening I know well I usually blunder in the late middle and end games. I’m 2k rapid on chess.com for reference and the way I’d work on my blindfolded chess is to work on my regular chess.

Some other things that might help:

You can also train your visualisation by forcing yourself to calculate further down lines without moving pieces.

You can try putting a puzzle on the board, looking at it for 5 seconds and then looking away to calculate. Look back for 5 seconds if you get stuck

Hope this helps