To work on this aspect of singing, it is best to work with a vocal teacher. In fact, if you are serious about singing, it is strongly recommended that you work with a teacher so as to learn the best technique right from the beginning. Find a teacher who is familiar with the style of music you are most interested in singing, but also keep your mind open to other styles of music.
There is much to be learned from great singers in all styles of music. Listening to great singers and imitating them is another excellent way to develop your voice, particularly by being aware of the sounds and sensations involved in making good sounds.