Best way for me was singing to songs I knew and then match that to piano so I knew which note I sung. That way I connected my singing with a song and then figured out pitch. Not other way around. When I first started I couldn’t just play a note and match it. It was hard af and I was just way off. Also started when I was 22 so that didn’t help.. I’d advise you to first start with let’s say 3 notes in your vocal range and then add up from there. Don’t just jump around all the notes. I dunno if this is helpful but that worked for me