How can I sing high notes and low notes, and have a good voice to wow an audience?

The best possible way you can fully achieve this is through voice lessons but if those aren't available then here are some tips: Practice more in those notes. the more you sing them, the easier it will be to get there later. But, keep in mind that every singer is different you may be made to sing certain notes that other people can't and vice versa Make sure you can give good breath support especially when you are singing notes you aren't used to. Stand tall and breath from your stomache. If you get to notes that become a little high or low don't move your head up or down. this is a mistake done by many people and it's very bad for you because it makes you do more work than you should. Keep your head straight and open the inside of your mouth more when you come to higher or lower notes. This makes the air flow more smoothly and it sounds better too. These are just a couple tips. There are many more ways to become a better singer that you can learn through voice lessons

For high notes you want to use your headvoice. You also want to use less and less air pressure for high notes. For low notes you want to use more air pressure.

You might want to look into private lessons, for example, from the local music store. A tutor might be able to address issues specifically. He or she should be able to help refine your technique.