If you read aloud for 1+ hour per day, after a year you’ll be a whole lot better. Anecdotally, reading aloud a variety of books (including some that push your kid’s abilities, some that are easy, and some familiar favorites) is far and away the most important thing you can do for his or her language development and development of reasoning.
If you really care about improving you can try to film yourself and watch it back, and you can try to come up with specific aspects of your performance to focus on.
But if you’re just trying your best and enjoying yourself, and you don’t intend to make performing for groups a career or something, just regular practice and a little bit of effort (and focusing/staying in the moment, rather than devoting half your attention to thinking about something else) should also be fine.
My eldest child is three and we both enjoy story time before bed; they are some of my fondest memories of my childhood. As I recall my father was a fantastic narrator and I feel I need to put some effort in!