Glad you asked. The minute you raise your voice, the screaming becomes the message rather than its content. It may not be possible to get your child to obey all the time or to understand, or even to listen. You need only keep Junior safe. You cannot control him, and have only a limited ability to mold his personality. A parent's love is usually thankless in the short run, but nothing's more rewarding long-term.
Be calm. Talk to your child in a calm, low voice. Explain to him how you expect him to behave. Do not scream or lose your temper.