Practice. You will get better with practice. It's normal to be nervous and make mistakes, especially in your first few live streams. But don't give up. Practice makes progress, and the more you do it, the more comfortable and confident you will be. Good luck!

If you are introducing a product, it's a must to read and study the product before you go Live.

I would strongly suggest to cut out all the "ermmm...; hmmm" from the vocabulary when doing the livestream, as it shows that you're nervous. Smiling and looking confident is always a good choice!