One of the most important aspects of singing is the ability to sing any desired pitch accurately. A good way to develop your pitching ability (called intonation) is to play or have someone else play notes on an instrument (e.g. piano) and copy the pitches with your voice. Some people find this easy immediately while others have to work at it for a while before they can do it. The most important thing is to listen carefully to the pitch being played and to trust your body to be able to produce that pitch.
Relax and let the sound come out naturally.
Enjoy your learning.