Leave the valves alone. Put the mouthpiece in the middle of your lips. Try to keep your lips together and blow some air through.
You want your lips to buzz in the wind. That buzz is what creates the sound of the trumpet. If it sounds like some sort of wildlife mating call you’re doing fine. You just have to get better at it before anyone – including you – will like the sound.
Tips for Playing Notes on the Trumpet
Experiment with how much air you’re blowing through, how fast you’re blowing, how much you’re using the muscles on the sides of your lips, where your tongue is inside your mouth and anything else you can think of. With any luck you’ll find that you’re able to get more the one note out of the Trumpet. That’s all explained on this other page.
If you still can’t get any sound at all click here for some possible solutions.
If the air is moving through the Trumpet, and you’re getting a really low, grumbly sound that seems way lower than anything like a Trumpet should sound click here.