How can I learn to hold the proper notes while playing.

For context, I got a Stawfire Also C from songbird as my first Ocarina, which may have been a more difficult first ocarina than I realised. This thing is amazing, but I've noticed that unlike my friend's ocarina, it is much more permissive to different blowing speeds, which would be great if I knew what I was doing, but I do not. Any time I am slowly practicing my scales with a tuner, I can usually get it right by guessing, but when I try to play any pieces, I am frequently more than 10 or 20 cents off the note, and it's harder for me to control it just right. My first guess on what to learn is maybe practicing relative pitch so I know what the notes are supposed to sound like and I can adjust, but at the moment I only know a general range which is a little too general to play with other in-tune instruments, so I'm looking for any advice that could help or if i should just carry on and keep practicing until I figure it out.